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Patrick Turner Patrick Turner is offline
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Default Audio Research VM220 and VT200 amps have serious design shortcomings......

Hi all,

I have a pair of VM220 200W monoblock amps here for a service, and a
stereo amp, VT200, 200W per channel.

Both sets of amps belonging to two different owners complained about
overheating tubes and burnt resistors and malfunctions.

My experience is not wonderful with all ARC amps because they end up
in my repair workshop because of their serious design shortcomings. I
have had to totally rewire a VT100 in the past to make it reliable and
easy to adjust bias settings.

But let me talk about the VM220 monblocs first, so that owners in
Australia might at least be able to live more peacefully with these
amps.

The VT220 has a sign on the rear panel which says the mains voltage
needed is 220Vac. There are probably 2 x 110Vac windings which would
be paralleled in the USA with 110Vac mains but here in Oz the nominal
mains = 240Vac which may exist of cold nights but otherwise often
measures 250Vrms during the day.

The result of mains = 250Vac with a mains tranny designed for 220Vac
is that the HT winding voltage rises and the B+ becomes +452Vdc
instead of +400Vdc.
All these ARC amps have screen supply voltage = plate supply voltage
so if the plate supply goes high, then the screen supply goes high
thus raising bias current alarmingly!

The multiple 470uF x 450V rated electrolytic B+ capacitors work with
+452Vdc across them.

The working measured heater voltage rises to 6.7Vac instead of the
correct 6.3Vac.

The amps come from the ARC factory with bias set for the USA
conditions where B+ would normally be just over +400Vdc.
When plugged used in Oz straight out of the box the bias currents in
each 6550 output tube is about 67mAdc, and the Pda per tube averages
about 31W at idle,
I have never seen any publically easily available information for the
biasing of all ARC amps and there is nothing printed on their amps
about biasing, and often the means of biasing is difficult and
extremely dangerous and confusing to many owners. I get so many ****ed
off owners of expensive ARC crap I have to say that ARC is overly
optimistic about their amps being able to survive very long, at least
in Oz.

I'm not sure what the recommended idle current should be in ARC amps
but it seems to me that Pda = 31W is much too high and invites
troubles.

In the pair of VM220 monos, I mounted a 16 ohm x 60W rated resistance
on a heatsink between the mains and output transformers. This is
connected in series with the 340Vrms HT winding and the diode bridge
charging the multiple electrocaps. I then biased each 6550 to 40mA at
idle and B+ settled at +430Vdc which s unlikely to bother caps rated
for 450Vdc. Pda + Pdg2 is now 17.2W, and the amp runs much cooler and
everything will last a lot better.

I will gurrantee the sound will NOT be degraded in any way, and I
found 200W was available at clipping with a sine wave, despite the
added series R in the B+ supply.

The VM220 was only produced between 2004 and 2008, and to me it was a
better design than VT100, VT120, VT200 etc.

Just why ARC would discontunue a better than before design is a
mystery, indicating their designers have **** for brains.

The VM220 has separate RC coupling of 6550 output tube grids to the
6N1P driver tubes. There are 8 pairs of voltmeter jacks allowing easy
monitoring of bias currents while twiddling each one of the 8 bias
pots located near each output tube, via a hole in the top plate.
However, its very easy to not find the pot's screwdriver slot because
their is no guide for a screwdriver, and there should be one along
with a philips headed pot shaft which should of course be metal and
much more rugged. But at least the VM220 has separate pots, one for
each tube, for acuurate bias setting.
The RC coupling is FAR MORE reliable than the stupid VT100 method ARC
has with coupled 6550 grids to driver tube cathodes, with biasing
voltage applied to driver cathode follower grids. When such cathode
follower tubes arc over inside because the driver tubes have too much
Ea betwen anode and cathode, the Vdc applied to output grids can go
very positive, and saturate output tubes which try to conduct 10 times
their idle current thus perhaps causing fuses to blow, but maybe not,
maybe burning out cathode resistors and or screen resistors.

There is no active protection circuitry in ARC amplifiers - its a
hostile form of negligence in this day and age where owners just wanna
plug and play without smoke ever happinging!!!!

Anyway, I suggest my little mod to the VM220 monos will allow them to
last a whole lot better than they otherwise might.

Now the owner of the VT200 just wants me to repair but not modify
because he says there isn't enough power.

The first dreadful and ****ing awful thing about the VT200 is the
weight. What on earth goes on in ARC designer's heads when they fail
dismally to to produce goods which cause serious spine problems every
time some unfit audiophile tries to move such a thing??????

The VT200 is like having 2 x VM220 inside the one box, but instead of
2 power trannies, there is just one big one.
But lifting VT200 is a two person job. The VM220 monos are too heavy,
but trying to deal with something twice this weight is a challenge,
and damned dangerous to health. The sooner someone sues the arse off
ARC, the better.

Anyway, The VT200 had caused at least two clouds of smoke to appear
while being used in Jindabyne, not far south of here.

I remove the 6mm al plate side covers to get access to the underside
of the 2 pcbs where there are 8 x 1 ohm resistors per channel, one for
each output tube, between each cathode and common connection to the
OPT secondary windings which are used for local cathode FB, rather
like Quad-II amps. These cathode R allow the monitoring of bias
current in each OP tube, but its a terrible shame one has to remove a
cover to check the bias current for each tube. Where are the plug in
test points??

I find two of these 2W cathode resistors have burnt to a crisp before
going open, hence there must have been two clouds of smoke.
I replaced one, and turned on the amp.
The tube with its open cathode 1r has no bias current, and I have yet
to see if the tube is stuffed, or the screen series R has also gone
open. But a tube nearby has a red glowing anode, although its current
is only 70mA, so probably its screen has overheated in the past and
screen wires have become warped deformed in the heat and the tube
function is ****ed.
But otherwise I find Ik = 60mA average everywhere with B+ at +445Vdc.
Heaters are at 6.7Vac, tolerable, but should be 6.3Vac.

Immediately I adjust bias down so Ik averages 33mA on the 14 out of
the 16 x 6550 tubes which appear to be working at all.

B= then rises to just over +450Vdc. ARC have all the VT200 tubes
laying horizontally so a natural breeze flows upwards past each tube
allowing good natural cooling. A single fan is fitted. It didn't come
on when the amp is turned on so I guess it only runs if things get
really hot.
I have only had the VT200 turned on for 15 minutes with only 14 tubes
working while my shed temperature is 30C on this summer day. Boy, I
got worried about the VT200 overall temperature. Fan didn't come on,
and even if it did, probably it is as useless as tits on a bull
because fans hardly ever do anything to prevent badly biased tubes.

The VT200 has the same awful crap method of direct coupled 6550 grids
to a 6922 cathode follower tube.
The 6922 have the same stupidly too high Ea to be reliable against
arcing.

The VT200 has a stupidly similar complex driver amp with many solid
state TO92 sized devices, mainly j-fets, for constant current sources.
In the past I have witnessed the failure and fusing of these fragile
bitsa crapology.
When is ARC going to ever learn to do without so many un-necessary
sordid state turds littering its tube boards?
There are also many adjust pots on the input-drive amp pcb and all
should NOT BE THERE, if ARC really knew how to build simply and
effectively.

The owner of the VT200 just wants a repair before selling the crap
ASAP, and without any mods.
This means the Electrolytics will be suject to a working Vdc slightly
above their stated rating.
BUT, at least I will have the damn amp running cooler, and heating of
electros and other circuitry located too close to output tubes will be
less severe. Looks like maybe 3 tubes need replacing. I found Svetlana
winged C 6550 have been fitted, and I don't know if these are
originals, or a set of replacements.

Now in the VT200 there are two bias adjust pots per channel. There are
holes for a small dia flat bladed screw driver to allow adjusting of
the bias pots. There are pcb mounted guide tubes for the screw driver.
But I found it very difficult to get a small screw driver to engauge
the the slot to make the adjustment because of poor alignment of guide
to pot. This would baffle non technical audiophiles.
But worst of all the VT200 only has ONE bias pot to adjust 4 x 6550
tubes, so the bias currents in each of the 4 tubes cannot ever be the
same. Even with a matched quad of 6550, there will be Iadc variations
for the one applied Vdc to the 4 grids. As the tubes age, they become
unmatched and it is not uncommon to find 4 output tubes which are
quite serviceble but which I require grid bias voltages which vary
within a range of say -53Vdc to -60Vdc in order to get the same Ikdc.
4 older but good tubes with the same applied grid bias voltage may
have Ikdc varying between 30mAdc and 80mAdc, so those with 30mAdc are
too cool, and those with 80mAdc are teetering on the brink of thermal
run-away. So one then MUST bias all 4 tubes at an average of say
33mAdc to allow for ageing drift, or for some clown who connects low
impedance insenstive speakers to the wrong labelled outlets, then has
a joint, too many beers, and turns up the volume to a silly level.
This is how some **** happens.
So the bias setting is determined by the tube which conducts the most
of the 4, and one must be sure to measure the Ikdc of each tube, and
all this is a painful thing which causes people to hate ARC.

ARC, it seems, don't need lessons in shooting themselves in the
foot.

I will proceed to repair the VT200, and hopefully it won't smoke while
the owner demonstrates its capabilities to someone willing to buy such
a thing.

I would have to say that on the VT200 ARC have improved their manner
of OPT matching to loads.
There are properly set out taps on the OPT sec to allow many properly
balanced speaker connections.
It means one may connect an 8 ohm speaker to where its says 4 ohms,
retain proper balance, and get good class A performance.

With 8 x 6550 per channel, and with Pda at idle = 31W, ( and plain
wrong, as explained above ), one has total Pda per channel = 248W, and
the maximum possible PURE class A1 is about 44% of 248W or 109W, and
this should be enough for anyone, but of course not for everyone.

The VT200 with high bias current setting will produce a total idling
heat = 700W+ for the two channels including the filament heater power.

So the VT200 and other similar concoctions are excellent amps if you
live in cold climates.

With bias set for 33mA average, the total Pda is only about 462W.

Class AB PO will be the same, but possible maximum pure class A =
approx 55W, also usually enough for anyone.

In all my experiences with local audiophiles there are none who
require 200W capability and most rarely have levels exceeding 5 watts
for more than a split second, so 2 x 6550 per channel for 50W class
AB1 usually gives superb performance and having another 6 x6550 tubes
per channel makes no difference to sound quality.

Regards to all, for the record, Patrick Turner.



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[email protected] arthrnyork@webtv.net is offline
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Posts: 81
Default Audio Research VM220 and VT200 amps have serious design shortcomings......

On Jan 25, 12:50*am, Patrick Turner wrote:
Hi all,

I have a pair of VM220 200W monoblock amps here for a service, and a
stereo amp, VT200, 200W per channel.

Both sets of amps belonging to two different owners complained about
overheating tubes and burnt resistors and malfunctions.

My experience is not wonderful with all ARC amps because they end up
in my repair workshop because of their serious design shortcomings. I
have had to totally rewire a VT100 in the past to make it reliable and
easy to adjust bias settings.

But let me talk about the VM220 monblocs first, so that owners in
Australia might at least be able to live more peacefully with these
amps.

The VT220 has a sign on the rear panel which says the mains voltage
needed is 220Vac. There are probably 2 x 110Vac windings which would
be paralleled in the USA with 110Vac mains but here in Oz the nominal
mains = 240Vac which may exist of cold nights but otherwise often
measures 250Vrms during the day.

The result of mains = 250Vac with a mains tranny designed for 220Vac
is that the HT winding voltage rises and the B+ becomes +452Vdc
instead of +400Vdc.
All these ARC amps have screen supply voltage = plate supply voltage
so if the plate supply goes high, then the screen supply goes high
thus raising bias current alarmingly!

The multiple 470uF x 450V rated electrolytic B+ capacitors work with
+452Vdc across them.

The working measured heater voltage rises to 6.7Vac instead of the
correct 6.3Vac.

The amps come from the ARC factory with bias set for the USA
conditions where B+ would normally be just over +400Vdc.
When plugged used in Oz straight out of the box the bias currents in
each 6550 output tube is about 67mAdc, and the Pda per tube averages
about 31W at idle,
I have never seen any publically easily available information for the
biasing of all ARC amps and there is nothing printed on their amps
about biasing, and often the means of biasing is difficult and
extremely dangerous and confusing to many owners. I get so many ****ed
off owners of expensive ARC crap I have to say that ARC is overly
optimistic about their amps being able to survive very long, at least
in Oz.

I'm not sure what the recommended idle current should be in ARC amps
but it seems to me that Pda = 31W is much too high and invites
troubles.

In the pair of VM220 monos, I mounted a 16 ohm x 60W rated resistance
on a heatsink between the mains and output transformers. This is
connected in series with the 340Vrms HT winding and the diode bridge
charging the multiple electrocaps. I then biased each 6550 to 40mA at
idle and B+ settled at +430Vdc which s unlikely to bother caps rated
for 450Vdc. Pda + Pdg2 is now 17.2W, and the amp runs much cooler and
everything will last a lot better.

I will gurrantee the sound will NOT be degraded in any way, and I
found 200W was available at clipping with a sine wave, despite the
added series R in the B+ supply.

The VM220 was only produced between 2004 and 2008, and to me it was a
better design than VT100, VT120, VT200 etc.

Just why ARC would discontunue a better than before design is a
mystery, indicating their designers have **** for brains.

The VM220 has separate RC coupling of 6550 output tube grids to the
6N1P driver tubes. There are 8 pairs of voltmeter jacks allowing easy
monitoring of bias currents while twiddling each one of the 8 bias
pots located near each output tube, via a hole in the top plate.
However, its very easy to not find the pot's screwdriver slot because
their is no guide for a screwdriver, and there should be one along
with a philips headed pot shaft which should of course be metal and
much more rugged. But at least the VM220 has separate pots, one for
each tube, for acuurate bias setting.
The RC coupling is FAR MORE reliable than the stupid VT100 method ARC
has with coupled 6550 grids to driver tube cathodes, with biasing
voltage applied to driver cathode follower grids. When such cathode
follower tubes arc over inside because the driver tubes have too much
Ea betwen anode and cathode, the Vdc applied to output grids can go
very positive, and saturate output tubes which try to conduct 10 times
their idle current thus perhaps causing fuses to blow, but maybe not,
maybe burning out cathode resistors and or screen resistors.

There is no active protection circuitry in ARC amplifiers - its a
hostile form of negligence in this day and age where owners just wanna
plug and play without smoke ever happinging!!!!

Anyway, I suggest my little mod to the VM220 monos will allow them to
last a whole lot better than they otherwise might.

Now the owner of the VT200 just wants me to repair but not modify
because he says there isn't enough power.

The first dreadful and ****ing awful thing about the VT200 is the
weight. What on earth goes on in ARC designer's heads when they fail
dismally to to produce goods which cause serious spine problems every
time some unfit audiophile tries to move such a thing??????

The VT200 is like having 2 x VM220 inside the one box, but instead of
2 power trannies, there is just one big one.
But lifting VT200 is a two person job. The VM220 monos are too heavy,
but trying to deal with something twice this weight is a challenge,
and damned dangerous to health. The sooner someone sues the arse off
ARC, the better.

Anyway, The VT200 had caused at least two clouds of smoke to appear
while being used in Jindabyne, not far south of here.

I remove the 6mm al plate side covers to get access to the underside
of the 2 pcbs where there are 8 x 1 ohm resistors per channel, one for
each output tube, between each cathode and common connection to the
OPT secondary windings which are used for local cathode FB, rather
like Quad-II amps. These cathode R allow the monitoring of bias
current in each OP tube, but its a terrible shame one has to remove a
cover to check the bias current for each tube. Where are the plug in
test points??

I find two of these 2W cathode resistors have burnt to a crisp before
going open, hence there must have been two clouds of smoke.
I replaced one, and turned on the amp.
The tube with its open cathode 1r has no bias current, and I have yet
to see if the tube is stuffed, or the screen series R has also gone
open. But a tube nearby has a red glowing anode, although its current
is only 70mA, so probably its screen has overheated in the past and
screen wires have become warped deformed in the heat and the tube
function is ****ed.
But otherwise I find Ik = 60mA average everywhere with B+ at +445Vdc.
Heaters are at 6.7Vac, tolerable, but should be 6.3Vac.

Immediately I adjust bias down so Ik averages 33mA on the 14 out of
the 16 x 6550 tubes which appear to be working at all.

B= then rises to just over +450Vdc. ARC have all the VT200 tubes
laying horizontally so a natural breeze flows upwards past each tube
allowing good natural cooling. A single fan is fitted. It didn't come
on when the amp is turned on so I guess it only runs if things get
really hot.
I have only had the VT200 turned on for 15 minutes with only 14 tubes
working while my shed temperature is 30C on this summer day. Boy, I
got worried about the VT200 overall temperature. Fan didn't come on,
and even if it did, probably it is as useless as tits on a bull
because fans hardly ever do anything to prevent badly biased tubes.

The VT200 has the same awful crap method of direct coupled 6550 grids
to a 6922 cathode follower tube.
The 6922 have the same stupidly too high Ea to be reliable against
arcing.

The VT200 has a stupidly similar complex driver amp with many solid
state TO92 sized devices, mainly j-fets, for constant current sources.
In the past I have witnessed the failure and fusing of these fragile
bitsa crapology.
When is ARC going to ever learn to do without so many un-necessary
sordid state turds littering its tube boards?
There *are also many adjust pots on the input-drive amp pcb and all
should NOT BE THERE, if ARC really knew how to build simply and
effectively.

The owner of the VT200 just wants a repair before selling the crap
ASAP, and without any mods.
This means the Electrolytics will be suject to a working Vdc slightly
above their stated rating.
BUT, at least I will have the damn amp running cooler, and heating of
electros and other circuitry located too close to output tubes will be
less severe. Looks like maybe 3 tubes need replacing. I found Svetlana
winged C 6550 have been fitted, and I don't know if these are
originals, or a set of replacements.

Now in the VT200 there are two bias adjust pots per channel. There are
holes *for a small dia flat bladed screw driver to allow adjusting of
the bias pots. There are pcb mounted guide tubes for the screw driver.
But I found it very difficult to get a small screw driver to engauge
the the slot to make the adjustment because of poor alignment of guide
to pot. This would baffle non technical audiophiles.
But worst of all the VT200 only has ONE bias pot to adjust 4 x 6550
tubes, so the bias currents in each of the 4 tubes cannot ever be the
same. Even with a matched quad of 6550, there will be Iadc variations
for the one applied Vdc to the 4 grids. As the tubes age, they become
unmatched and it is not uncommon to find 4 output tubes which are
quite serviceble but which I require grid bias voltages which vary
within a range of say -53Vdc to -60Vdc in order to get the same Ikdc.
4 older but good tubes with the same applied grid bias voltage may
have Ikdc varying between 30mAdc and 80mAdc, so those with 30mAdc are
too cool, and those with 80mAdc are teetering on the brink of thermal
run-away. So one then MUST bias all 4 tubes at an average of say
33mAdc to allow for ageing drift, or for some clown who connects low
impedance insenstive speakers to the wrong labelled outlets, then has
a joint, too many beers, and turns up the volume to a silly level.
This is how some **** happens.
So the bias setting is determined by the tube which conducts the most
of the 4, and one must be sure to measure the Ikdc of each tube, and
all this is a painful thing which causes people to hate ARC.

ARC, it seems, don't need lessons in shooting themselves in the
foot.

I will proceed to repair the VT200, and hopefully it won't smoke while
the owner demonstrates its capabilities to someone willing to buy such
a thing.

I would have to say that on the VT200 ARC have improved their manner
of OPT matching to loads.
There are properly set out taps on the OPT sec to allow many properly
balanced speaker connections.
It means one may connect an 8 ohm speaker to where its says 4 ohms,
retain proper balance, and get good class A performance.

With 8 x 6550 per channel, and with Pda at idle = 31W, ( and plain
wrong, as explained above ), one has total Pda per channel = 248W, and
the maximum possible PURE class A1 is about 44% of 248W or 109W, and
this should be enough for anyone, but of course not for everyone.

The VT200 with high bias current setting will produce a total idling
heat = 700W+ for the two channels including the filament heater power.

So the VT200 and other similar concoctions are excellent amps if you
live in cold climates.

With bias set for 33mA average, the total Pda is only about 462W.

Class AB PO will be the same, but possible maximum pure class A =
approx 55W, also usually enough for anyone.

In all my experiences with local audiophiles there are none who
require 200W capability and most rarely have levels exceeding 5 watts
for more than a split second, so 2 x 6550 per channel for 50W class
AB1 usually gives superb performance and having another 6 x6550 tubes
per channel makes no difference to sound quality.

Regards to all, for the record, Patrick Turner.


Does ARC have a warranty repair center in Oz ?
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Watt? Me worry? Watt? Me worry? is offline
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Posts: 58
Default Audio Research VM220 and VT200 amps have serious design shortcomings......

Hi RATs!

ARC builds status symbols for buyers with more money than brains. They
are legion.

ARC is a business. In business, designers are not in charge of much,
unless they also are the owner. But, owner/designers are not all
geniuses. Some may think they are...

______


I have worked on old tube gear. The 110Vac it was designed for is
hidden in the 122.5 Vac in my wall socket.

I put pairs of resistors, one on each end of the power transformer
primary, until the measured at the pins heater voltage is 6.3V, MAX. 6
volts is adequate. (OK, 12.6 volts MAX, as required)

Yes, the Rs take up space and create heat. No, that excess power and
heat never get into the unit.

Putting Rs between the PT and the OPT maximizes the damage done by the
too high voltage and only addresses part of the problem.

Once the heaters are not frying the tubes, I proceed to tune the
circuits.

Often, the circuits are well within specs, once the heater voltage is
tamed.

Sixteen 6550 tubes is not design, it is style. Style sells. People buy
sizzle, not steak.

Some ARC owners never complain. They never turn them on. They look
cool, that is all that is required.

They tell the tech they listen all the time, but, only get it fixed to
sell it.

______

Patrick, are you near the floods? I thought you were in western Oz,
but, I imagine more than I remember, these days.

Music is a joy. I used to know some interesting stuff about that, too.

Happy Ears!

Al

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Patrick Turner Patrick Turner is offline
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Posts: 3,964
Default Audio Research VM220 and VT200 amps have serious design shortcomings......

On Jan 25, 2:45*pm, "Watt? Me worry?" wrote:
Hi RATs!

ARC builds status symbols for buyers with more money than brains. They
are legion.

ARC is a business. In business, designers are not in charge of much,
unless they also are the owner. But, owner/designers are not all
geniuses. Some may think they are...

______

I have worked on old tube gear. The 110Vac it was designed for is
hidden in the 122.5 Vac in my wall socket.

I put pairs of resistors, one on each end of the power transformer
primary, until the measured at the pins heater voltage is 6.3V, MAX. 6
volts is adequate. (OK, 12.6 volts MAX, as required)

Yes, the Rs take up space and create heat. No, that excess power and
heat never get into the unit.

Putting Rs between the PT and the OPT maximizes the damage done by the
too high voltage and only addresses part of the problem.

Once the heaters are not frying the tubes, I proceed to tune the
circuits.

Often, the circuits are well within specs, once the heater voltage is
tamed.

Sixteen 6550 tubes is not design, it is style. Style sells. People buy
sizzle, not steak.

Some ARC owners never complain. They never turn them on. They look
cool, that is all that is required.

They tell the tech they listen all the time, but, only get it fixed to
sell it.

______

Patrick, are you near the floods? I thought you were in western Oz,
but, I imagine more than I remember, these days.

Music is a joy. I used to know some interesting stuff about that, too.

Happy Ears!

Al


Thanks for your thoughts Al.

In the two VM220 ARC amps I have here now the series R between HT
winding and diodes for B+ is made of 6 x 100 ohms in parallel then
siliconed to heatsink and held tight with bolted bracket off the
chassis. The 16 ohms series R is quite sufficient to lower B+ to a
safe level even if Ik in each tube is adjusted to a mild 33mAdc.
if the Ik dc is adjusted to 67mA, the the B+ reduces further but the
heat liberated in the resistor is still not excessive, and not as much
as any one of the 8 x 6550 tubes. The actual value of such a series R
is critical in that just the right value for B+ reduction and low Pd
is chosen.
Another way is to use say 2 x 60uF plastic motor start caps in series
to make 30uF off the rectifiers, each rated for 400Vdc, then install a
choke to the total of 3,750uF which ARC have as the capacitance
between OPT CT and 0V. There can be high ripple with no Pd in the
30uF, and Vdc is then lowered without heat.
The choke need only be 1.7H. Easy, but that all involves more
work&expense than other methods.

I am on high ground well away from huge regions of Oz which are so
flat that if rivers rise 5 metres there are lakes of water extending
many miles each side of the rivers. Oz has slow cycles of rainfal
between severe droughts lasting maybe 10 years and then rainy seasons
with biblical rains and floods lasting a year in some places.

But the flooding troubles of Oz at this time are nothing but slightly
inconvenient puddles of water when compared to what happened last year
in northern Pakistan where 20 million ppl were ****ed up big time, and
there was no help from anyone, and there is corruption in govt, and
there are the ****ing Taliban, and there is desease and famine and the
whole full catastrophe. Bangladesh also cops water **** and all these
places have far more troubles than us where ppl just clean up, get a
Govt hand out, and buy new furniture and wait another 10 years for the
same thing to happen again. There is not enough high ground for ppl to
live, and increase in population meant planners began to allow
development in flood prone areas and the style of houses has changed
to low level single storey on a concrete floor slab instead of the
traditional style with living on a first floor with level 3 metres
above ground, so that the whole ground floor area is a nice cool place
to be during summer, and one uses upstairs only for sleeping at night
and staying above most floods.

Meanwhile the price of farm produce such as fruit and vegetables has
risen hugely, and everyone has to pay.

Patrick Turner.



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Patrick Turner Patrick Turner is offline
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Posts: 3,964
Default Audio Research VM220 and VT200 amps have serious design shortcomings......

On Jan 25, 2:45*pm, "Watt? Me worry?" wrote:
Hi RATs!

ARC builds status symbols for buyers with more money than brains. They
are legion.

ARC is a business. In business, designers are not in charge of much,
unless they also are the owner. But, owner/designers are not all
geniuses. Some may think they are...

______

I have worked on old tube gear. The 110Vac it was designed for is
hidden in the 122.5 Vac in my wall socket.

I put pairs of resistors, one on each end of the power transformer
primary, until the measured at the pins heater voltage is 6.3V, MAX. 6
volts is adequate. (OK, 12.6 volts MAX, as required)

Yes, the Rs take up space and create heat. No, that excess power and
heat never get into the unit.

Putting Rs between the PT and the OPT maximizes the damage done by the
too high voltage and only addresses part of the problem.

Once the heaters are not frying the tubes, I proceed to tune the
circuits.

Often, the circuits are well within specs, once the heater voltage is
tamed.

Sixteen 6550 tubes is not design, it is style. Style sells. People buy
sizzle, not steak.

Some ARC owners never complain. They never turn them on. They look
cool, that is all that is required.

They tell the tech they listen all the time, but, only get it fixed to
sell it.

______

Patrick, are you near the floods? I thought you were in western Oz,
but, I imagine more than I remember, these days.

Music is a joy. I used to know some interesting stuff about that, too.

Happy Ears!

Al


BTW, I forgot to mention that ARC amps with lotsa multiple 6550 can
sound very good despite all you say about style, and agony, which
people a putton on all the time in many ways including when they buy
an ARC amp.

But lets not be fooled, any keen audio amatuer may get excellent sound
in his lounge with just 2 x 6550 or even less if he knows what he's
doing. I once got into trouble with an audio club for saying the ARC
reference 600 monbloc was like a Rolls Royce with 16 wheels. Kind of
excessively capable.

But we live in times where every man may live as well a a king if he
so choses in the Land Of the Free, the Land of Glory, Land of
Opportunity, etc, and more BS etc, Good 'Ol USof A, where the
doctors and dentists and lawyers are outrageously expensive.

Whoopee, gimme all those 6550, we demand it, they all cry.

Set up properly, the 6550 plus a decent drive amp can make pass music
without damaging its soul.

Patrick Turner.


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[email protected] arthrnyork@webtv.net is offline
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Default Audio Research VM220 and VT200 amps have serious design shortcomings......

On Jan 25, 6:40*pm, Patrick Turner wrote:
On Jan 25, 2:45*pm, "Watt? Me worry?" wrote:





Hi RATs!


ARC builds status symbols for buyers with more money than brains. They
are legion.


ARC is a business. In business, designers are not in charge of much,
unless they also are the owner. But, owner/designers are not all
geniuses. Some may think they are...


______


I have worked on old tube gear. The 110Vac it was designed for is
hidden in the 122.5 Vac in my wall socket.


I put pairs of resistors, one on each end of the power transformer
primary, until the measured at the pins heater voltage is 6.3V, MAX. 6
volts is adequate. (OK, 12.6 volts MAX, as required)


Yes, the Rs take up space and create heat. No, that excess power and
heat never get into the unit.


Putting Rs between the PT and the OPT maximizes the damage done by the
too high voltage and only addresses part of the problem.


Once the heaters are not frying the tubes, I proceed to tune the
circuits.


Often, the circuits are well within specs, once the heater voltage is
tamed.


Sixteen 6550 tubes is not design, it is style. Style sells. People buy
sizzle, not steak.


Some ARC owners never complain. They never turn them on. They look
cool, that is all that is required.


They tell the tech they listen all the time, but, only get it fixed to
sell it.


______


Patrick, are you near the floods? I thought you were in western Oz,
but, I imagine more than I remember, these days.


Music is a joy. I used to know some interesting stuff about that, too.


Happy Ears!


Al


BTW, I forgot to mention that ARC amps with lotsa multiple 6550 can
sound very good despite all you say about style, and agony, which
people a putton on all the time in many ways including when they buy
an ARC amp.

But lets not be fooled, any keen audio amatuer may get excellent sound
in his lounge with just 2 x 6550 or even less if he knows what he's
doing. I once got into trouble with an audio club for saying the ARC
reference 600 monbloc was like a Rolls Royce with 16 wheels. Kind of
excessively capable.

But we live in times where every man may live as well a a king if he
so choses in the Land Of the Free, the Land of Glory, Land of
Opportunity, *etc, and more BS etc, *Good 'Ol USof A, where the
doctors and dentists and lawyers are outrageously expensive.

Whoopee, gimme all those 6550, we demand it, they all cry.

Set up properly, the 6550 plus a decent drive amp can make pass music
without damaging its soul.

Patrick Turner.- Hide quoted text -

- Show quoted text -


In the Land of the Free aka as Home of the Brave, when the mains
voltage is is off 10--20% we use Variacs . And no need to monkey
around with unnecessary 'modifucations' .
  #7   Report Post  
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Patrick Turner Patrick Turner is offline
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Default Audio Research VM220 and VT200 amps have serious design shortcomings......

On Jan 28, 1:06*am, wrote:
On Jan 25, 6:40*pm, Patrick Turner wrote:





On Jan 25, 2:45*pm, "Watt? Me worry?" wrote:


Hi RATs!


ARC builds status symbols for buyers with more money than brains. They
are legion.


ARC is a business. In business, designers are not in charge of much,
unless they also are the owner. But, owner/designers are not all
geniuses. Some may think they are...


______


I have worked on old tube gear. The 110Vac it was designed for is
hidden in the 122.5 Vac in my wall socket.


I put pairs of resistors, one on each end of the power transformer
primary, until the measured at the pins heater voltage is 6.3V, MAX. 6
volts is adequate. (OK, 12.6 volts MAX, as required)


Yes, the Rs take up space and create heat. No, that excess power and
heat never get into the unit.


Putting Rs between the PT and the OPT maximizes the damage done by the
too high voltage and only addresses part of the problem.


Once the heaters are not frying the tubes, I proceed to tune the
circuits.


Often, the circuits are well within specs, once the heater voltage is
tamed.


Sixteen 6550 tubes is not design, it is style. Style sells. People buy
sizzle, not steak.


Some ARC owners never complain. They never turn them on. They look
cool, that is all that is required.


They tell the tech they listen all the time, but, only get it fixed to
sell it.


______


Patrick, are you near the floods? I thought you were in western Oz,
but, I imagine more than I remember, these days.


Music is a joy. I used to know some interesting stuff about that, too..


Happy Ears!


Al


BTW, I forgot to mention that ARC amps with lotsa multiple 6550 can
sound very good despite all you say about style, and agony, which
people a putton on all the time in many ways including when they buy
an ARC amp.


But lets not be fooled, any keen audio amatuer may get excellent sound
in his lounge with just 2 x 6550 or even less if he knows what he's
doing. I once got into trouble with an audio club for saying the ARC
reference 600 monbloc was like a Rolls Royce with 16 wheels. Kind of
excessively capable.


But we live in times where every man may live as well a a king if he
so choses in the Land Of the Free, the Land of Glory, Land of
Opportunity, *etc, and more BS etc, *Good 'Ol USof A, where the
doctors and dentists and lawyers are outrageously expensive.


Whoopee, gimme all those 6550, we demand it, they all cry.


Set up properly, the 6550 plus a decent drive amp can make pass music
without damaging its soul.


Patrick Turner.- Hide quoted text -


- Show quoted text -


In the Land of the Free aka as Home of the Brave, *when the mains
voltage is is off 10--20% we use Variacs . And no need to monkey
around with unnecessary 'modifucations' .- Hide quoted text -

- Show quoted text -


Indeed a variac is one other solution. But to run a pair of VM220 one
would need a variac rated for 1kVA and then if someone turns the
control knob the wrong way......

The mods I'm doing are rather minimal, and easily bypassed, and a heck
of a lot cheaper than buying a suitable variac or well rated 240V:220V
step down tranny although making up a box as Alaex suggests and which
I explained before with a 240V : 24V transformer within and rated for
120VA is probably the easiest way to avoid any mods and a high cost.
When i talk soon to the owner of the VT200 which he does not want
modded, I will explain all and give him his options, but until he
decides the bias will be adjusted to reduce the Ia considerably to
prevent tubes burning out so easily.

He has said he wants to sell his VT200 because he thinks there is not
enough power and that he might get ARC 300W monoblocs instead. Well
maybe he'll have the same problems so I need to explain all and let
the guy decide.

Some 5 years back I had a client with a very heavy 70W per channel
stereo VAC amp which he'd bought on E-bay fairly cheaply. it had 8 x
300B in it. Soon it began to smoke and blow fuses and hum badly.
Tubes had individual cathode bias RC networks but although this
regulated the Ia fairly well, the idle condition was Pda = 37W
average, and of course 300B started failing soon and it still sounded
well with 3 dead tubes because there was enough NFB and there was at
least one 300B working on each side of the PP circuit on both
channels. It came to me shortly after I heard it and there were 4 dead
or faulty 300B. This amp had had a small fire around one 300B socket
from excessive heat; a whole square inch of the 1/8" PCN had become
charcoal. A bodgy repair had been done, and solder joints had gone
dry.

I gutted the whole amp and put in my own simpler circuit but with much
better B+ filtering and set it to to make 50W AB max with all tubes
idling at less than 28W.
Hum vanished, and no more smoke because I removed most of the design
faults VAC had so unkindly included.
Its never missed a beat since. There is plenty of power, and sound is
blameless. Active protection is fitted and if any 300B conducts too
much Ia for longer than 4 seconds, the amp turns off automatically.

Patrick Turner.
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Big Bad Bob Big Bad Bob is offline
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Default Audio Research VM220 and VT200 amps have serious design shortcomings......

On 01/25/11 06:18, Patrick Turner so witilly quipped:
My point is that one should not have to buy any additional mains
tranny nor do any mods. The ARC amps should be ableto be set for all
countries and mains voltages.



It might make a lot of sense if amp makers were to use switching power
supplies in these high end tube amps, and avoid the power transformer
altogether. Chances are it would significantly lower the cost of the
unit at the same time (and not affect the sound). You could even have a
tube rectifier and LC filter on the output side of the switcher, if
people demand it. I would guess it would cost about the same as a
typical computer power supply to make something like that. And it
wouldn't weigh as much as a boat anchor. And you wouldn't get 'heater
hum' in the cathode circuits (assuming regulated DC heater supply).

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Patrick Turner Patrick Turner is offline
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Default Audio Research VM220 and VT200 amps have serious design shortcomings......

snip for brevity,


In the Land of the Free aka as Home of the Brave, *when the mains
voltage is is off 10--20% we use Variacs . And no need to monkey
around with unnecessary 'modifucations' .


Technicians and do it yourselfers, maybe, but the vast majority of
users do exactly what his user does: plug it in and turn it on.- Hide quoted text -



The vast majority of users are technically illiterate, through no
fault of their own.

They cannot be blamed for buying ARC and other major "reputable" brand
names of audio gear while thinking they can use it without special
mains arrangements to get reliability if the mains voltage is 13.7%
above the labelled input mains voltage on the unit they buy, ie,
252Vrms instead of the labelled 220Vrms.

The damn hi-brow makers AND low brow makers SHOULD ensure that users
are made aware of the pitfalls of incorrect mains voltages. But they
all know any mention of anything technical or of any possible negative
outcomes is detrimental to sales figures. They think its better users
burn their gear to bits, with an attitude of utter carelessness about
their customers.

Usually most makers might test their gear during the prototyping
process so that mains voltages of +10% or -10% may be applied
indefinately while retaining 90% of the reliability of the item when
the mains voltage is exactly as specified.

ARC and many other makers in the US and in China etc fail this golden
rule dismally.

When the local shop Duratone Hi-Fi began importing Jolida amplifiers
they found the B+ in their UL amps with EL34 or 6550 would rise to
+530Vdc and way above the normal 470V and with a big increase in Ia,
and Pda went just above rated limits. So after several cloud-of-smoke
events and angry customers they were forced to modify all the stocks
they imported with a changed arrangement of electrolytic caps which
shorted out. But they also then had to re-bias any all amps to a lower
Ia to avoid a high Pda, and this allowed the B+ to rise even more. I
had the job of fixing two Jolidas after OPT failures, probably caused
by tubes saturating, heating OPT primaries, and then causing shorted
turns.
In one case O opened up tha Jolida 502 OPT to see where/how the short
had occurred, and as stunned my the ****ing lousy quality of the OPT
winding method, so it didn't take much to make the OPTs fail.
The Jolida brand is a is a US-China joint venture, and both the
Chinese and their US exploiters don't give a **** about quality.

The correct way to provide for mains voltage selection is as
follows...

There should be TWO mains tranny windings, both meant for 120Vrms, but
so Bmax is 1 Tesla even with 50Hz and 135vrms.
Taps should be placed on both for Common, 100V, 110V, 120V.

Then you can get low loss matches of parallel windings for 100V, 110V,
120V.

Series connection can give 200V, 210V, 220V, 230V, 240V.

B+ should never rise to more than 95% of the Vdc working voltage
rating of electrocaps even if 1/2 the recommended Ia is used for bias
and if the mains voltage rises 5% above the nominal value of the
country in which the amp is used.

So, in Oz, where mains is sometimes 255V, and nominal voltage is
240Vrms, and where cap rating is +450V, then cap working voltage must
never rise to above
+428Vdc. The best way tfor any maker to avoid problems of exceeding
Elcap V rating is to use caps in series, say rated for 350Vdc each so
that rating is +700vdc and there is never a problem. And the easiest
best way to achieve this is with a voltage doubler type of rectifier.
See my website for many examples.

Nicholson brand soldering irons made in China are widely sold in Oz
and cost about $25 for 80W versions. They are designed to run on
220Vac.
But here and in other parts of Oz we have 255Vac mains and the irons
won't last longer than a month if just plugged in here without a step
down tranny or a series resistor, which I uses, in a metal box under
the bench.

I fused 3 Chinese irons years ago until I made the step down
resistance box and then when I know there is about 210Vac at the iron,
they run fine for maybe 2 years or more used daily for long periods in
my workshop, with the hot end inside an open jam tin as a guard
agaisnt this falling on the hot iron.
screwed to the bench.
I had used Weller brand mains irons but could never get more than 12
months from them and they cost 3 times as much as the Chinese types.

The ARC uses hi-temp soldering which probably is Rohs complient, ie,
lead free, and of course difficult to solder with irons meant for for
old 35/65 standard solder.
But with the Chinese irons plugged straight into my 250V mains here I
found I could remove the open circuit cathode and screen resistors off
the ARC pcbs, and then solder in replacements using old type solder.

The ARC VT200 amp has what appear to be 3 Watt wire wound 100 ohms
series screen resistors. There appear to be old style wire wound.
There are carbon composition 1 ohm x 1W resistors between the 6550
cathodes and the OPT speaker secondary winding which is arranged to
provide 10% local cathode feedback to the two lots of 4 x 6550 on each
side of the PP circuit, ie, in a very similar manner to a Quad-II
amplifier.

To generate enough heat in a 1W x 1 ohm R to make it burst into
flames, one might have to have say 2W of power for some time so the
current must be 1.41 Amps, a huge amount considering the tube curves
indicate 0.5A max with grid bias at 0.0Vdc. To make a 3W x 100 ohm
also fuse open with 6W, then I must be 244 mA, way above the normal
6mA ort working screen current. So obviously when tubes decide to go
beserko, rather high amounts of energy are generated in the tube, and
sometimes it is in the form of very strong RF oscillations which the
"stopper" resistors don't stop. Many makers like ARC and and ALL
others afaik just don't give a **** about the damage shorting output
tubes may cause, and they never would bother to fit active protection
schemes against collateral caused by a failing OP tube.

Perhaps the ARC 100 ohm and 1 ohm resistors are *meant to fuse open*,
ie are fusible resistors made to go open but its all secret ARC
business.

On many amps I have put in a normal metal film 270 ohm x 1/4W
resistance between B+ and the screens. If it flames there is usualy
very little damage, and there is no need to replace it with a special
resistance type which is dfficult to get. If Ig2 rises from say 6mA to
12mA, Pd = 0.39W, and the 270 ohms will last OK if the time spent at
0.39W is a small duty cycle.ARC have what looks like a loose fitting
fibreglass sleeve around the 1 ohm cathode resistances. This falls
apart once fried by a flaming resistance. The presence ofthe sleeving
is somewhat useless IMHO, and partly prevents ppl easily measuring Ik
after removing the side covers off the amp to examine the idle
currents in each and every output tube.

Patrick Turner.



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GRe GRe is offline
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Default Audio Research VM220 and VT200 amps have serious design shortcomings......


"Patrick Turner" wrote in message
...

[...]

The vast majority of users are technically illiterate, through no
fault of their own.

They cannot be blamed for buying ARC and other major "reputable" brand
names of audio gear while thinking they can use it without special
mains arrangements to get reliability if the mains voltage is 13.7%
above the labelled input mains voltage on the unit they buy, ie,
252Vrms instead of the labelled 220Vrms.



Obviously (on paper) ARC's operate within spec even at .au supply.

VT200 Power requirements: 105-125VAC, 60Hz (210-250VAC, 50Hz);
990W at rated output; 1200W maximum; 680W at idle.
(not from the manufacturer's site)

VT200 MKII Power requirements: 105-125VAC, 60Hz (210-250VAC, 50Hz);
990W at rated output; 1200W maximum; 680W at "idle".
Complete spec, see: http://www.audioresearch.com/vt200.html

VM220 Power requirements: 105-125VAC, 60Hz (210-250VAC, 50Hz);
620W at rated output; 900W maximum; 400W at "idle".
Complete spec, see: http://www.audioresearch.com/VM220.html


The damn hi-brow makers AND low brow makers SHOULD ensure that users
are made aware of the pitfalls of incorrect mains voltages. But they
all know any mention of anything technical or of any possible negative
outcomes is detrimental to sales figures. They think its better users
burn their gear to bits, with an attitude of utter carelessness about
their customers.


A bit hard to find but ARC actually say something about it, quote:

"Factors which can shorten tube life include inadequate
ventilation, overdriving loudspeakers at continuously high
volume levels, severely fluctuating A.C. line conditions (e.g.
sagging line voltage during summer peaks of air-conditioning
demand), or severe interference pulses or electromagnetic
interference. Power-conditioning products such as line filters,
isolation transformers and the like may or may not help sonic
performance, particularly when used with power amplifiers;
contact your dealer for professional advice. A dedicated 15-amp
or 20-amp A.C. circuit for your power amplifier is the most
effective solution for power-starved audio systems".

[...]

Regards,
Gio









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Patrick Turner Patrick Turner is offline
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Default Audio Research VM220 and VT200 amps have serious design shortcomings......

On Jan 28, 10:03*pm, "GRe" wrote:
"Patrick Turner" wrote in message

...



[...]

The vast majority of users are technically illiterate, through no
fault of their own.


They cannot be blamed for buying ARC and other major "reputable" brand
names of audio gear while thinking they can use it without special
mains arrangements to get reliability if the mains voltage is 13.7%
above the labelled input mains voltage on the unit they buy, ie,
252Vrms instead of the labelled 220Vrms.


Obviously (on paper) ARC's operate within spec even at .au supply.

VT200 Power requirements: 105-125VAC, 60Hz (210-250VAC, 50Hz);
990W at rated output; 1200W maximum; 680W at idle.
(not from the manufacturer's site)


Unfortunately, ARC designers do not realise their idiocy of
"theoretical on paper functionality".

You are right about the mains power draw with VT200; its quite high to
maximise the class A1 working, but I will always keep saying that
biasing multiple 6550 tubes with just one fixed grid bias voltage and
allowing Pda to be 31W and allowing B+ to be just above the electro
cap working voltage in a box where temperatures rise dangerously on
hot summer days where we often get 35C room temp is a recipe for
trouble. Here I am fixin' trouble, right?

VT200 MKII Power requirements: 105-125VAC, 60Hz (210-250VAC, 50Hz);
990W at rated output; 1200W maximum; 680W at "idle".
Complete spec, see:http://www.audioresearch.com/vt200.html

VM220 Power requirements: 105-125VAC, 60Hz (210-250VAC, 50Hz);
620W at rated output; 900W maximum; 400W at "idle".
Complete spec, see:http://www.audioresearch.com/VM220.html


So where is any recomendation to adjust the bias currents to comply
with a safe reliable Pda?

There is none. All too often I find hi-end makers are much too
optimistic.



The damn hi-brow makers AND low brow makers SHOULD ensure that users
are made aware of the pitfalls of incorrect mains voltages. But they
all know any mention of anything technical or of any possible negative
outcomes is detrimental to sales figures. They think its better users
burn their gear to bits, with an attitude of utter carelessness about
their customers.


A bit hard to find but ARC actually say something about it, quote:

"Factors which can shorten tube life include inadequate
ventilation,


The VT200 and VM220 have adequate natural ventilation without reliance
in any fan, although the VT200 does have a fan, just one, but because
tubes quickly drift away from being a matched quad at purchase, the
practice of using one bias voltage applied to 4 x 6550 means that Pda
may average say 31Watts, but may vary between 20W and 45W, and OP
tubes mysteriously just expire thermally because there is insufficient
bias monitoring let alone any visual indication of bias current
condition or any active protection circuits to turn the amp OFF when a
6550 begins to conduct excessive Idc. Not IF, but WHEN, ok

overdriving loudspeakers at continuously high
volume levels,


What a meaningless statement this one is!!!!!!!!!!!!

Just exactly what is meant? Where are the technical terms.

Will ARC over heat their tubes if driven for 1 hour in a room at 35C
with mains at 250Vac, and with an 8 ohm resistance or other reactive 8
ohm load and at any level up to clipping with a sine wave?
Assuming all speakers have a region where actual Z is below the
nominal, how do their amps cope with a 6 ohm resistance load connected
to the 8 ohm terminations and run at clipping indefinately?

severely fluctuating A.C. line conditions (e.g.
sagging line voltage during summer peaks of air-conditioning
demand),


Again, wheat is meant? If the mains voltage was at 250Vac with no air
con or room heating etc, then with air con or room heating or someone
welding in the garage, maybe mains might drop 10% which should not
affect the amp adversly although ther max PO will fall and clipping
will occur at a lower PO level.
Sudden RISE in mains voltage from 250V to 270V could spell disaster
though.

or severe interference pulses or electromagnetic
interference.


Again, where do they quantify the the interference?

Seems to me they are desperate to blame amp failure on something other
than their own shortcomings.

Power-conditioning products such as line filters,
isolation transformers and the like may or may not help sonic
performance, particularly when used with power amplifiers;



Haha ha, wht a load of ********. The aforesaid products are used
specifcally to help control imperfect mains supplies.

But of course few known power conditioning devices would affect any
linear PSU or the sound of any amp such as made by ARC.


contact your dealer for professional advice. A dedicated 15-amp
or 20-amp A.C. circuit for your power amplifier is the most
effective solution for power-starved audio systems".


Power starving is seldom a problem in a modern domestic situation in a
western country.

Here we easily have at least 10A capable domestic power wiring with
240V which allows 2,400Watts of draw and one will find Vmains falls
less than 5%.
Obviously, in the USA one should have the same 2,400W capability so
one might want 20A x 120V circuits.
I've never had any trouble running a pair of my 300W monoblocks with a
total of 24 x 6550 tubes. No special wiring was needed.

I don't expect anyone to agree with me about what ARC and many other
makers should do about their designs.

All these makers are severely egotistical and believe that their ****
don't stink, but I know both theirs and mine does stink, and I have
nothing to loose by pointing out to all their products could be
improved greatly. I include circuitry in my creations to prevent
clouds of smoke, the other guys don't bother.

Patrick Turner.


Regards,
Gio


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Patrick Turner Patrick Turner is offline
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Default Audio Research VM220 and VT200 amps have serious design shortcomings......

On Jan 29, 4:53*am, flipper wrote:
On Fri, 28 Jan 2011 00:53:49 -0800 (PST), Patrick Turner

wrote:
snip for brevity,


In the Land of the Free aka as Home of the Brave, when the mains
voltage is is off 10--20% we use Variacs . And no need to monkey
around with unnecessary 'modifucations' .


Technicians and do it yourselfers, maybe, but the vast majority of
users do exactly what his user does: plug it in and turn it on.- Hide quoted text -


The vast majority of users are technically illiterate, through no
fault of their own.


"Technically illiterate" is a buzz phrase that has no meaning unless
qualified. Users may be "technically illiterate" about the quantum
mechanics of LED light emission but they are technically literate
enough to drive cars, operating iPods, iPhones, and many other
'technical' devices.


The astronauts who went to the moon in 1969 did not have to know how
to repair/modify or service their vehicle.
So complete technical literacy isn't needed for a moon trip.
But I bet those astronauts knew more about their rocket than the
average audiophile knows about his audio gear!!!!!!!

Most of my customers know **** all about how the amps they buy work.
If asked to describe how it all works, they cannot, and biasing is
something poorly understood and many get it very WRONG unless I make
sure it is impossible to bias any tube with too much current.

It is my duty of care to protect my customers from themselves. It is
my customers' right to obtain something they buy from me which is easy
to live with, needing almost zero understanding of anything technical,
and which will never put smoke int their loungerooms.


They cannot be blamed for buying ARC and other major "reputable" brand
names of audio gear while thinking they can use it without special
mains arrangements to get reliability if the mains voltage is 13.7%
above the labelled input mains voltage on the unit they buy, ie,
252Vrms instead of the labelled 220Vrms.


Actually, yes, they can be 'blamed'.

For example, my nephew decided to try the 'wrong' mains setting on a
computer power supply. Why he did it is another story but the PSU is
blown. His fault.



I've lost count of the number of times I have had to repair US made
gear which ppl here have bought on E-bay, then plugged in to 240
without a step down tranny.
A good amp design will just blow a fuse, but not the rectifier diodes.



Btw, 252V is 14.5% above 220V, not 13.7%.


Indeed, but so what?



The question here would be, who represented it would work on what and,
then, what did it end up on?


Huh???

The damn hi-brow makers AND low brow makers SHOULD ensure that users
are made aware of the pitfalls of incorrect mains voltages. But they
all know any mention of anything technical or of any possible negative
outcomes is detrimental to sales figures. They think its better users
burn their gear to bits, with an attitude of utter carelessness about
their customers.


Bullcorn


You are free to believe what you like....

A distributor might, figuring 'it's the manufacturers responsibility'
(more likely ignorance), but no reputable manufacturer ever knowingly
sells equipment that is doomed to fail as the loss of reputation and
warranty service would far exceed any short term gain.


They may claim they don't knowingly sell gear that fails all too
easily, but it fails. ARC is such an old venerable brand, they think
they can let their amps be "conditionally reliable", wheras I would
always look for ways of making my product unconditionally reliable,
like making an amp unconditionally stable.

A few 'fooled you' sales is peanuts compared to the future 'bad
reputation' loss of sales.


Using ARC amps here with 250V mains puts the amps at their most
severely stressed operational condition especially where room temp may
be 35C on a hot day.
I just want ppl to know.

I would prefer they designed their amps so this high stress is
avoidable.

Usually most makers might test their gear during the prototyping
process so that mains voltages of +10% or -10% may be applied
indefinately while retaining 90% of the reliability of the item when
the mains voltage is exactly as specified.


ARC and many other makers in the US and in China etc fail this golden
rule dismally.


Oh really? And just how the hell do you think they work here then?


I see the results of poor amplifier design shortcomings on my work
bench all too often.

So, really, yes, **** happens.



255V is not +-10% of 220V (the rating you stated was on the amp).

When the local shop Duratone Hi-Fi began importing Jolida amplifiers
they found the B+ in their UL amps with EL34 or 6550 *would rise to
+530Vdc and way above the normal 470V and with a big increase in Ia,
and Pda went just above rated limits. So after several cloud-of-smoke
events and angry customers they were forced to modify all the stocks
they imported with a changed arrangement of electrolytic caps which
shorted out. But they also then had to re-bias any all amps to a lower
Ia to avoid a high Pda, and this allowed the B+ to rise even more.


Btw, did it ever occur to you that if there are so many problems in Oz
that maybe there's something 'unusual' about Oz?


There is nothing unusual about Oz. OK, so we have mains which goes up
to 255Vac sometimes.

But if you were here, you might think you were in a state of the Union
because life here is a similar standard to that in the USA.

Ppl here have thought of selling Oz to the USA, but they were told it
more or less already is in USA hands so we don't need to sell it.
The profits of many US owned businesses go back to the US....


As of 2000 your nominal mains voltage is *supposed* to be 230V +10%
-6%.

I can't prove but I suspect the places running a hot 255V (the number
you gave) are occasionally spiking above even that and taking the amps
even further out of spec.


Indeed mains often measures 255Vrms with my Fluke meter.

ARC should take this into account, and adjust their designs to cope
better and keep their amps out of my workshop where i san see them,
inspect them, and then write horrible things about them.

But all ARC owners in Oz ought to know about the horribilities I find.

Then the solutions may be found and offered, so music and happiness
can flow without smoke and repair bills.

I
had the job of fixing two Jolidas after OPT failures, probably caused
by tubes saturating, heating OPT primaries, and then causing shorted
turns.
In one case O opened up tha Jolida 502 OPT to see where/how the short
had occurred, and as stunned my the ****ing lousy quality of the OPT
winding method, so it didn't take much to make the OPTs fail.
The Jolida brand is a is a US-China joint venture, and both the
Chinese and their US exploiters don't give a **** about quality.


While I respect your opinion on how to make OPTs survive a nuclear
blast you are not the world's arbiter of 'quality'.


Nobody is the world's arbiter of anything. I am in the industry of am
making. I do believe in self regulation. This means I will expose
others to scrutiny. It means owners and buyers of amps get a better
deal. And while I talk openly and transparently about all matters
technical I have a 22MB website crammed with ideas.

All makers should welcome my input of constructive criticisms, for
they only stand to gain by making improvements rather than letting
their products become overly complex and too conditional for
reliability.


The correct way to provide for mains voltage selection is as
follows...


There should be TWO mains tranny windings, both meant for 120Vrms, but
so Bmax is 1 Tesla even with 50Hz and 135vrms.
Taps should be placed on both for Common, 100V, 110V, 120V.


Then you can get low loss matches of parallel windings for 100V, 110V,
120V.


Series connection can give 200V, 210V, 220V, 230V, 240V.


The vast majority of the world is standardized in the ranges of
110-120 and 220-230, which is why it's so common to see
"international" transformer primaries rated '115V' and '230V' 50/60Hz.

That means they actually run a little to the high side in the US but
we don't have things blowing up all over the place.

B+ should never rise to more than 95% of the Vdc working voltage
rating of electrocaps even if 1/2 the recommended Ia is used for bias
and if the mains voltage rises 5% above the nominal value of the
country in which the amp is used.


Your own criteria fails in Oz since the 'nominal value' there is
officially given in AS 60038 as 230V and 255V is well over 5% by more
than twice at 10.9%. It doesn't even work for the 240V you *think* is
nominal as 255V is 6.25% over that.


I can't write an industry standard in the time for an email here.

I sure could not propose anything ARC or anyone else would adopt.

Everyone hates being told how to make their gear.


Design engineers in the rest of the world, though, might believe your
government's specifications.


Only a complete fool would build an amp to comply with a government's
spec rather than what is really the case in any country.

In most old radios for the Oz market there were always 3 mains input
selections, 220V, 240V, and 260V.

So where a radio was bought by someone way down a country road with
low mains, he could use the 220V setting. But if he moved to town the
setting was forgotten, but although the city voltage of 240V was and
remains to be so common, the radio rarely would smoke if used with the
wrong setting.

There was no silly attempt to run the 6V6 output tube at high Pda.


So, in Oz, where mains is sometimes 255V, and nominal voltage is
240Vrms,


Your 'nominal' is *not* 240V, it's 230V. Call up Canberra and ask
them.


I have never ever seen 230V here and here is where I live in Canberra.
Sometimes on really cold evenings with high heating power used by all
the mains goes down to 237V.

I cannot alter an established situation.

Those running 240V do so on the grounds it's 'within spec' but it's
*not* nominal and 255V, the number you provided, doesn't meet spec.
It's not 'a lot' out but it is, nevertheless, out.


and where cap rating is +450V, then cap working voltage must
never rise to above
+428Vdc. The best way tfor any maker to avoid problems of exceeding
Elcap V rating is to use caps in series, say rated for 350Vdc each so
that rating is +700vdc and there is never a problem. And the easiest
best way to achieve this is with a voltage doubler type of rectifier.
See my website for many examples.


Nicholson brand soldering irons made in China are widely sold in Oz
and cost about $25 for 80W versions. They are designed to run on
220Vac.
But here and in other parts of Oz we have 255Vac mains and the irons
won't last longer than a month if just plugged in here without a step
down tranny or a series resistor, which I uses, in a metal box under
the bench.


I fused 3 Chinese irons years ago


I guess they didn't plan on them being run 16% over rated.


My guess is that they were made for Chinese condtions, 220Vac, and
sloppy marketeers don't give a ****, and just sell what can be sold.


until I made the step down
resistance box and then when I know there is about 210Vac at the iron,
they run fine for maybe 2 years or more used daily for long periods in
my workshop, with the hot end inside an open jam tin as a guard
agaisnt this falling on the hot iron.
screwed to the bench.
I had used Weller brand mains irons but could never get more than 12
months from them and they cost 3 times as much as the Chinese types.


They probably didn't plan on them being run overrated either.


I returned two failed Weller irons to the Cooper Tools factory in
Albury-Wodonga. They were very keen to inspect irons which had failed.
Probably all soldering irons last years if only used for 1 hour in 6
months, but I often have mine running hot all day, year after year.
Weller sent me two new irons as replacements and tried to tell me the
salt content in water used for making a clay mix used with the iron
wire used in the heating coil had caused the early iron failure, and
despite my resistance box to lower the applied voltage.
I tried telling them to make irons with 12V heating coils of thicker
wire and supply a transformer, but they said that would make it
impossible to compete on price.

The replacements failed and I went to te Chinese product which works
just fine for years if one keeps the applied mains voltage at no more
than 220Vac.

So I can get the Chinese irons to last real good except for the mains
lead from wall socket to iron. Unfortunately the quality of the
ordinary 3 core mains flex has become down graded in just about all
gear compared to previous years. So after 6 months the strands of
copper wire in the mains cables fatigues, arcs, and goes open and
sometimes short circuits and blows switch box circuit breakers. And
all this while oneis using the iron and holding the cable while it
****s itself up.
I have 8 amp circuit breakers for my work bench which limits what I
can use, but I found it necessary because of crap I have to use.
The solution is to wrap a pile of tape around the lead where it enters
the plastic handle of the iron so that the cable bends over a much
wider radius. Its slightly more awkward, but of course a net
improvement.


The ARC uses hi-temp soldering which probably is Rohs complient, ie,
lead free, and of course difficult to solder with irons meant for for
old 35/65 standard solder.
But with the Chinese irons plugged straight into my 250V mains here I
found I could remove the open circuit cathode and screen resistors off
the ARC pcbs, and then solder in replacements using old type solder.


Well, you could get a hotter iron instead of over volting a lower
rated one.


I way well have to get an iron designed to run hotter for the non-lead
soldering.

So far I have not needed to.


The ARC VT200 amp has what appear to be 3 Watt wire wound 100 ohms
series screen resistors. There appear to be old style wire wound.
There are carbon composition 1 ohm x 1W resistors between the 6550
cathodes and the OPT speaker secondary winding which is arranged to
provide 10% local cathode feedback to the two lots of 4 x 6550 on each
side of the PP circuit, ie, in a very similar manner to a Quad-II
amplifier.


To generate enough heat in a 1W x 1 ohm R to make it burst into
flames, one might have to have say 2W of power for some time so the
current must be 1.41 Amps, a huge amount considering the tube curves
indicate 0.5A max with grid bias at 0.0Vdc. To make a 3W x 100 ohm
also fuse open with 6W, then I must be 244 mA, way above the normal
6mA ort working screen current. So obviously when tubes decide to go
beserko, rather high amounts of energy are generated in the tube, and
sometimes it is in the form of very strong RF oscillations which the
"stopper" resistors don't stop. Many makers like ARC and and ALL
others afaik just don't give a **** about the damage shorting output
tubes may cause, and they never would bother to fit active protection
schemes against collateral caused by a failing OP tube.


Protection circuitry is a wonderful thing. My Sony SS 'theater amp'
(had to have something that could decode the TV S/PDIF) has all sorts
of 'smarts' to 'protect' me from doing something stupid except it's
the 'protection' circuitry that's gone insane and keeps shutting down
the amp.


And so often in solid state amps its the fuse which blows last after
several power transistors and a few diodes and driver transistors and
resistors have fused, and the protection circuit did not detect or
react to the presence and effect of a shorted speaker cable at low
volume levels.

I think all SS amp makers have signed a secret Declaration Of
Incompetence, or DOI, and this forbids any one of them to place output
terninals far enough apart to stop strands of speaker cables touching.
I have seen speaker wires owners have used where they have bared the
wires for use with a kitchen knife but have bared far too much, and
never bothered to twist all the strands together. Then they have move
the system around and turned the speakers around thus twisting the two
bared wires together, all without the slightest idea of what may
result. And also forbidden by the secret manufacturers' Agreement Of
Bull****, ie, AOB, is the provision of a circuit costing 50c with two
ICs which detects the presence of a load less than 2 ohms at any level
of operation and which reacts by TURNING THE ****ING AMP OFF but then
displaying a red LED beside a sign which says,
"You have a faulty speaker or cable".

I raise my hat politely to all the fuctards and their shortcomings
because they give me a chance to compete in the market place.....

Never expect to see such a quote in 'Stereophile', a place where
embarrassment is always elegantly sidestepped.


Patrick Turner.

  #13   Report Post  
Posted to rec.audio.tubes
Patrick Turner Patrick Turner is offline
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Posts: 3,964
Default Audio Research VM220 and VT200 amps have serious design shortcomings......

On Jan 29, 7:27*am, flipper wrote:
On Fri, 28 Jan 2011 12:03:55 +0100, "GRe"





wrote:

"Patrick Turner" wrote in message
....


[...]


The vast majority of users are technically illiterate, through no
fault of their own.


They cannot be blamed for buying ARC and other major "reputable" brand
names of audio gear while thinking they can use it without special
mains arrangements to get reliability if the mains voltage is 13.7%
above the labelled input mains voltage on the unit they buy, ie,
252Vrms instead of the labelled 220Vrms.


Obviously (on paper) ARC's operate within spec even at .au supply.


VT200 Power requirements: 105-125VAC, 60Hz (210-250VAC, 50Hz);
990W at rated output; 1200W maximum; 680W at idle.
(not from the manufacturer's site)


VT200 MKII Power requirements: 105-125VAC, 60Hz (210-250VAC, 50Hz);
990W at rated output; 1200W maximum; 680W at "idle".
Complete spec, see:http://www.audioresearch.com/vt200.html


VM220 Power requirements: 105-125VAC, 60Hz (210-250VAC, 50Hz);
620W at rated output; 900W maximum; 400W at "idle".
Complete spec, see:http://www.audioresearch.com/VM220.html


Those specs are technically 'not quite right' as 'harmonization'
specifies 230VAC +- 10% for a range of 207VAC-253VAC. In the former
240VAC countries the spec is 230VAC +10% -6% and in the 220VAC
countries it's 230VAC +6 -10, so they didn't have to change a blessed
thing, which results in the same 'fully harmonized' 230VAC +- 10% spec
as far as equipment manufacturers go. Maybe ARC is using 'round
numbers'.

Further, country power specs are 'on the grid' and not your wall
outlet. "Service voltage" (outlet) can be down to 85% of nominal,
which is why design engineers see operating specs that don't 'match'
the country power spec. I mean as far as steady state voltage goes.
The 'every day' problems are transients and brownouts.

To cover operating conditions the amp should cover 185VAC to 253VAC
but you might put the 'country power' range on the label to avoid
confusion.

Something doesn't jive, though, because Patrick says the amp's label
states 220VAC and that isn't consistent with the above spec. That
leads me to believe it might be a 'pre harmonization' amp that was
intended for 220VAC continental Europe use.

And therein lies a problem because harmonization only 'pretends' to
harmonize by inventing a new spec that's simply wide enough to
encompass the existing power systems but it didn't actually change a
blessed thing on the ground. In theory that's 'not a problem' for
*new* designs, which should take into account the extended +-10%
range, but it leads to a perception problem that "we're all on the
same power now so what works in France should work in the U.K." Except
(for the most part) France was and is still 220VAC +-6% while the U.K
was and is still 240VAC +-6% so what was 'once upon a time' built for
220VAC is over voltaged on 240VAC.

All 'harmonization' did was to 'force' manufacturers into making
equipment that works in both 220VAC and 240VAC countries, which they
could and usually did do on their own by either complying with both
specs (one means being transformer taps as Patrick mentioned) or
making models specific to the export region, but, in the process, it
created confusion by pretending something changed. It's also a pain in
the butt for manufacturer's because they can no longer 'fine tune' a
product for the actual mains power as it has to be the mythical, and
wider (more difficult to design for), 'harmonized' voltage of 230VAC
+-10%.



The damn hi-brow makers AND low brow makers SHOULD ensure that users
are made aware of the pitfalls of incorrect mains voltages. But they
all know any mention of anything technical or of any possible negative
outcomes is detrimental to sales figures. They think its better users
burn their gear to bits, with an attitude of utter carelessness about
their customers.


A bit hard to find but ARC actually say something about it, quote:


"Factors which can shorten tube life include inadequate
ventilation, overdriving loudspeakers at continuously high
volume levels, severely fluctuating A.C. line conditions (e.g.
sagging line voltage during summer peaks of air-conditioning
demand), or severe interference pulses or electromagnetic
interference. Power-conditioning products such as line filters,
isolation transformers and the like may or may not help sonic
performance, particularly when used with power amplifiers;
contact your dealer for professional advice. A dedicated 15-amp
or 20-amp A.C. circuit for your power amplifier is the most
effective solution for power-starved audio systems".


[...]


Regards,
Gio- Hide quoted text -


- Show quoted text -- Hide quoted text -

- Show quoted text -


I suspect ARC may have switched to 220V chinese made power trannies.

All I do know is that ppl here buy ARC stuff and don't care about the
mains voltage and then smoke happens.

It is insanely stupid to expect a large heavy box full of very hot
vacuum tubes to last well when the mains voltage is too high, and the
biasing method is so stupid, and there is no active protection if one
or more tubes goes into thermal run-away.

As long as ppl here in Oz understand that there can be problems and
that there are solutions, I have done all I can.

Patrick Turner.
  #14   Report Post  
Posted to rec.audio.tubes
Patrick Turner Patrick Turner is offline
external usenet poster
 
Posts: 3,964
Default Audio Research VM220 and VT200 amps have serious design shortcomings......

On Jan 29, 3:32*pm, flipper wrote:
On Fri, 28 Jan 2011 17:40:48 -0800 (PST), Patrick Turner





wrote:
On Jan 29, 7:27*am, flipper wrote:
On Fri, 28 Jan 2011 12:03:55 +0100, "GRe"


wrote:


"Patrick Turner" wrote in message
...


[...]


The vast majority of users are technically illiterate, through no
fault of their own.


They cannot be blamed for buying ARC and other major "reputable" brand
names of audio gear while thinking they can use it without special
mains arrangements to get reliability if the mains voltage is 13.7%
above the labelled input mains voltage on the unit they buy, ie,
252Vrms instead of the labelled 220Vrms.


Obviously (on paper) ARC's operate within spec even at .au supply.


VT200 Power requirements: 105-125VAC, 60Hz (210-250VAC, 50Hz);
990W at rated output; 1200W maximum; 680W at idle.
(not from the manufacturer's site)


VT200 MKII Power requirements: 105-125VAC, 60Hz (210-250VAC, 50Hz);
990W at rated output; 1200W maximum; 680W at "idle".
Complete spec, see:http://www.audioresearch.com/vt200.html


VM220 Power requirements: 105-125VAC, 60Hz (210-250VAC, 50Hz);
620W at rated output; 900W maximum; 400W at "idle".
Complete spec, see:http://www.audioresearch.com/VM220.html


Those specs are technically 'not quite right' as 'harmonization'
specifies 230VAC +- 10% for a range of 207VAC-253VAC. In the former
240VAC countries the spec is 230VAC +10% -6% and in the 220VAC
countries it's 230VAC +6 -10, so they didn't have to change a blessed
thing, which results in the same 'fully harmonized' 230VAC +- 10% spec
as far as equipment manufacturers go. Maybe ARC is using 'round
numbers'.


Further, country power specs are 'on the grid' and not your wall
outlet. "Service voltage" (outlet) can be down to 85% of nominal,
which is why design engineers see operating specs that don't 'match'
the country power spec. I mean as far as steady state voltage goes.
The 'every day' problems are transients and brownouts.


To cover operating conditions the amp should cover 185VAC to 253VAC
but you might put the 'country power' range on the label to avoid
confusion.


Something doesn't jive, though, because Patrick says the amp's label
states 220VAC and that isn't consistent with the above spec. That
leads me to believe it might be a 'pre harmonization' amp that was
intended for 220VAC continental Europe use.


And therein lies a problem because harmonization only 'pretends' to
harmonize by inventing a new spec that's simply wide enough to
encompass the existing power systems but it didn't actually change a
blessed thing on the ground. In theory that's 'not a problem' for
*new* designs, which should take into account the extended +-10%
range, but it leads to a perception problem that "we're all on the
same power now so what works in France should work in the U.K." Except
(for the most part) France was and is still 220VAC +-6% while the U.K
was and is still 240VAC +-6% so what was 'once upon a time' built for
220VAC is over voltaged on 240VAC.


All 'harmonization' did was to 'force' manufacturers into making
equipment that works in both 220VAC and 240VAC countries, which they
could and usually did do on their own by either complying with both
specs (one means being transformer taps as Patrick mentioned) or
making models specific to the export region, but, in the process, it
created confusion by pretending something changed. It's also a pain in
the butt for manufacturer's because they can no longer 'fine tune' a
product for the actual mains power as it has to be the mythical, and
wider (more difficult to design for), 'harmonized' voltage of 230VAC
+-10%.


The damn hi-brow makers AND low brow makers SHOULD ensure that users
are made aware of the pitfalls of incorrect mains voltages. But they
all know any mention of anything technical or of any possible negative
outcomes is detrimental to sales figures. They think its better users
burn their gear to bits, with an attitude of utter carelessness about
their customers.


A bit hard to find but ARC actually say something about it, quote:


"Factors which can shorten tube life include inadequate
ventilation, overdriving loudspeakers at continuously high
volume levels, severely fluctuating A.C. line conditions (e.g.
sagging line voltage during summer peaks of air-conditioning
demand), or severe interference pulses or electromagnetic
interference. Power-conditioning products such as line filters,
isolation transformers and the like may or may not help sonic
performance, particularly when used with power amplifiers;
contact your dealer for professional advice. A dedicated 15-amp
or 20-amp A.C. circuit for your power amplifier is the most
effective solution for power-starved audio systems".


[...]


Regards,
Gio- Hide quoted text -


- Show quoted text -- Hide quoted text -


- Show quoted text -


I suspect ARC may have switched to 220V chinese made power trannies.


The only reason you 'suspect' that is it's the only 'suspicion' which
would comply with your perennial determination to declare everyone
else idiots and crooks.


Not everyone is a crook or an idiot.

Sometimes perfectly wonderful people can design amps which would
easily withstand one or two serious improvements.

I managed to complete the servicing on the VT200 this afternoon.

But they have a 27 ohm 1/4 watt plus what appears to be a 1ohm
resistance between the anodes and OPT primary connection. It looks
like an old fashioned carbon comp resistance but may indeed be
inductive, but anyway two had exploded apart from too much heat. I saw
no coil of wire. The other good ones measured 1 ohm.
So during initial testing measured an average of 67mA of anode
current without the screen current, so maybe the Ia + Ig2 was 75mA and
Pda even higher than I thought it was.

I found that they DON''T have 1 ohm R in the cathode circuits but have
0.2 ohm which are 5 watt rated, well made and none were faulty. Only
one screen resistance had failed. I set the bias by measuring the
voltage across 4 x 0.54 ohm 5W resistors in the anode supplies to each
PP 1/2 of each channel. Bias currents varied by a max of 50% and ther
maximum bias currents determined the final overal setting. Pda is now
less than 20W max per tube.
The tubes were all serviceable. Two which had cooked their series
resistances and one which I found to glow with a red plate all seem OK
and seem stable and happy with the lower bias current.



God only knows why they'd deliberately make it 220VAC, and mark it
220VAC, when everyone 'knows' the harmonized voltage is 230VAC and
their published spec complies with harmonized 230VAC. That is, only
God and you 'knows'.


I don't believe there is any God except the God Of Triodes, and he
sends me a bad electric shock if I ever spout bull****.

I certainly would never want anyone to think I was on a par with some
imagined deity.

I'm just a humble bloke, doin my job, and tryna keep ppl in music
without smoke, noise, and distortion or sullen silence.


All I do know is that ppl here buy ARC stuff and don't care about the
mains voltage and then smoke happens.


Go ahead and tell me how you've done a survey of all ARC amps sold in
Oz and they all have 220VAC markings on them and burned up.


Well, I have at least one colleague who is never surprised with smoke
emanations from ARC amps.

I don't get to see many ARC amps, but those I do see have burned out
parts in them.

The pair of VM220 have a 220Vac sticker. Not very prominent, but there
it is, probably because there are two 110V windings in series.


Then explain how you've investigated and determined it's impossible
the amp was intended for continental Europe 220VAC mains, since the
blooming thing is MARKED 220VAC, but somehow ended up in Oz. (and it
isn't a 'U.S.' marking because our 'large appliance' voltage is
240VAC)


Much stuff people don't want elsewhere in the world ends up in Oz
after its has been sold on E-bay.

I would say much has 110V setting for the USA. Nearly every audiophile
I know has something he bought on E-bay and he has a 240V:110V step
transformer. With preamps it is not critical but with power amps it
only become critical if the mains voltage is too high while ppl ignore
it.


Just to be clear, I don't have the answer to those questions either
but then I'm not running around calling people idiots and crooks when
I don't know for sure.


Well, today while setting the bias on the VT200, I have to remove the
cover allowing access to the two current sensing R in the anode supply
circuit.
Then I have t hold a pair of voltmeter prods to the two ends of a
resistance, read a volt meter while turning a bias pot where the screw
driver doesn't wanto to easily engage the slot. The bias pot is a
single turn and bias setting is very touchy. But I manage because I
have worked so long with tube gear. But an audiophile novice might
find it a terrible struggle and slip with prods and cause a fuse to
blow or he gets a bad electric shock trying to do 3 things at once.
ARC seem to have glued on some flimsy plastic sheeting around the
current sensing R as they have anticipated troubles ppl could have,
and probably in response to those who told them of the difficulties or
the shocks they'd had.

What should be there is a separate adjust pot for each 6550, along
with 16 pairs of sockets to test the bias currents for the 16 tubes in
the VT200.
The best place for such test point and screw adjust heads is on the
front panel of the amp so owners never have to remove a cover or move
the amp to bias it.
A re-green LED to show the bias condition is wise.


It is insanely stupid to expect a large heavy box full of very hot
vacuum tubes to last well when the mains voltage is too high, and the
biasing method is so stupid, and there is no active protection if one
or more tubes goes into thermal run-away.


As long as ppl here in Oz understand that there can be problems and
that there are solutions, I have done all I can.


Well, we can hope no one's listening because if you're not 100% right
on each accusation you're opening yourself up for a defamation
lawsuit.


Its a wonder nobody has sued ARC for causing spinal injuries.

I'm here to promoe ARC product improvement, and never to be too
harsh.

No doubt 1% of people contemplating the purchase of some ARC tube amp
will do a search and our discussions will come to their screens.
People in the USA and where mains voltage is correct may rest easier
than here where mains voltage can be too high.

The crew who run Audigon.com discussion group must have found what I
had to say way too contentious to publish.
Moderated groups are somewhat censored. But here we may discuss
problems and solutions freely.

Other problems in VT100, 120, 200 and derivatives could do with a big
fix by ARC.

I wish them well.

Patrick Turner.
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Default Audio Research VM220 and VT200 amps have serious design shortcomings......

On Jan 28, 8:40*pm, Patrick Turner wrote:
On Jan 29, 7:27*am, flipper wrote:





On Fri, 28 Jan 2011 12:03:55 +0100, "GRe"


wrote:


"Patrick Turner" wrote in message
....


[...]


The vast majority of users are technically illiterate, through no
fault of their own.


They cannot be blamed for buying ARC and other major "reputable" brand
names of audio gear while thinking they can use it without special
mains arrangements to get reliability if the mains voltage is 13.7%
above the labelled input mains voltage on the unit they buy, ie,
252Vrms instead of the labelled 220Vrms.


Obviously (on paper) ARC's operate within spec even at .au supply.


VT200 Power requirements: 105-125VAC, 60Hz (210-250VAC, 50Hz);
990W at rated output; 1200W maximum; 680W at idle.
(not from the manufacturer's site)


VT200 MKII Power requirements: 105-125VAC, 60Hz (210-250VAC, 50Hz);
990W at rated output; 1200W maximum; 680W at "idle".
Complete spec, see:http://www.audioresearch.com/vt200.html


VM220 Power requirements: 105-125VAC, 60Hz (210-250VAC, 50Hz);
620W at rated output; 900W maximum; 400W at "idle".
Complete spec, see:http://www.audioresearch.com/VM220.html


Those specs are technically 'not quite right' as 'harmonization'
specifies 230VAC +- 10% for a range of 207VAC-253VAC. In the former
240VAC countries the spec is 230VAC +10% -6% and in the 220VAC
countries it's 230VAC +6 -10, so they didn't have to change a blessed
thing, which results in the same 'fully harmonized' 230VAC +- 10% spec
as far as equipment manufacturers go. Maybe ARC is using 'round
numbers'.


Further, country power specs are 'on the grid' and not your wall
outlet. "Service voltage" (outlet) can be down to 85% of nominal,
which is why design engineers see operating specs that don't 'match'
the country power spec. I mean as far as steady state voltage goes.
The 'every day' problems are transients and brownouts.


To cover operating conditions the amp should cover 185VAC to 253VAC
but you might put the 'country power' range on the label to avoid
confusion.


Something doesn't jive, though, because Patrick says the amp's label
states 220VAC and that isn't consistent with the above spec. That
leads me to believe it might be a 'pre harmonization' amp that was
intended for 220VAC continental Europe use.


And therein lies a problem because harmonization only 'pretends' to
harmonize by inventing a new spec that's simply wide enough to
encompass the existing power systems but it didn't actually change a
blessed thing on the ground. In theory that's 'not a problem' for
*new* designs, which should take into account the extended +-10%
range, but it leads to a perception problem that "we're all on the
same power now so what works in France should work in the U.K." Except
(for the most part) France was and is still 220VAC +-6% while the U.K
was and is still 240VAC +-6% so what was 'once upon a time' built for
220VAC is over voltaged on 240VAC.


All 'harmonization' did was to 'force' manufacturers into making
equipment that works in both 220VAC and 240VAC countries, which they
could and usually did do on their own by either complying with both
specs (one means being transformer taps as Patrick mentioned) or
making models specific to the export region, but, in the process, it
created confusion by pretending something changed. It's also a pain in
the butt for manufacturer's because they can no longer 'fine tune' a
product for the actual mains power as it has to be the mythical, and
wider (more difficult to design for), 'harmonized' voltage of 230VAC
+-10%.


The damn hi-brow makers AND low brow makers SHOULD ensure that users
are made aware of the pitfalls of incorrect mains voltages. But they
all know any mention of anything technical or of any possible negative
outcomes is detrimental to sales figures. They think its better users
burn their gear to bits, with an attitude of utter carelessness about
their customers.


A bit hard to find but ARC actually say something about it, quote:


"Factors which can shorten tube life include inadequate
ventilation, overdriving loudspeakers at continuously high
volume levels, severely fluctuating A.C. line conditions (e.g.
sagging line voltage during summer peaks of air-conditioning
demand), or severe interference pulses or electromagnetic
interference. Power-conditioning products such as line filters,
isolation transformers and the like may or may not help sonic
performance, particularly when used with power amplifiers;
contact your dealer for professional advice. A dedicated 15-amp
or 20-amp A.C. circuit for your power amplifier is the most
effective solution for power-starved audio systems".


[...]


Regards,
Gio- Hide quoted text -


- Show quoted text -- Hide quoted text -


- Show quoted text -


I suspect ARC may have switched to 220V chinese made power trannies.

All I do know is that ppl here buy ARC stuff and don't care about the
mains voltage and then smoke happens.

It is insanely stupid to expect a large heavy box full of very hot
vacuum tubes to last well when the mains voltage is too high, and the
biasing method is so stupid, and there is no active protection if one
or more tubes goes into thermal run-away.

As long as ppl here in Oz understand that there can be problems and
that there are solutions, I have done all I can.

Patrick Turner.- Hide quoted text -

- Show quoted text -


Chances are, ARC may be doing just that ! US-manufactured
transformers are ver-r-r-y dear these days . And besides, creeping AC
mains voltages are becoming a problem here , as well . What is
historically known as a ' 110 ' volts AC slowly became 117,
120,125,128 ... I measured what is very close to 130 volts on some
occasions . A good and serious manufacturer should have built his
equipment with proper VAC input settings in order to accomodate
variations anywhere in the entire world . Reality has a habit of
biting you . Better safe than sorry !


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Default Audio Research VM220 and VT200 amps have serious design shortcomings......

On Jan 29, 9:00*pm, flipper wrote:
On Sat, 29 Jan 2011 06:17:26 -0800 (PST), wrote:
On Jan 28, 8:40 pm, Patrick Turner wrote:
On Jan 29, 7:27 am, flipper wrote:


On Fri, 28 Jan 2011 12:03:55 +0100, "GRe"


wrote:


"Patrick Turner" wrote in message
...


[...]


The vast majority of users are technically illiterate, through no
fault of their own.


They cannot be blamed for buying ARC and other major "reputable" brand
names of audio gear while thinking they can use it without special
mains arrangements to get reliability if the mains voltage is 13.7%
above the labelled input mains voltage on the unit they buy, ie,
252Vrms instead of the labelled 220Vrms.


Obviously (on paper) ARC's operate within spec even at .au supply.


VT200 Power requirements: 105-125VAC, 60Hz (210-250VAC, 50Hz);
990W at rated output; 1200W maximum; 680W at idle.
(not from the manufacturer's site)


VT200 MKII Power requirements: 105-125VAC, 60Hz (210-250VAC, 50Hz);
990W at rated output; 1200W maximum; 680W at "idle".
Complete spec, see:http://www.audioresearch.com/vt200.html


VM220 Power requirements: 105-125VAC, 60Hz (210-250VAC, 50Hz);
620W at rated output; 900W maximum; 400W at "idle".
Complete spec, see:http://www.audioresearch.com/VM220.html


Those specs are technically 'not quite right' as 'harmonization'
specifies 230VAC +- 10% for a range of 207VAC-253VAC. In the former
240VAC countries the spec is 230VAC +10% -6% and in the 220VAC
countries it's 230VAC +6 -10, so they didn't have to change a blessed
thing, which results in the same 'fully harmonized' 230VAC +- 10% spec
as far as equipment manufacturers go. Maybe ARC is using 'round
numbers'.


Further, country power specs are 'on the grid' and not your wall
outlet. "Service voltage" (outlet) can be down to 85% of nominal,
which is why design engineers see operating specs that don't 'match'
the country power spec. I mean as far as steady state voltage goes.
The 'every day' problems are transients and brownouts.


To cover operating conditions the amp should cover 185VAC to 253VAC
but you might put the 'country power' range on the label to avoid
confusion.


Something doesn't jive, though, because Patrick says the amp's label
states 220VAC and that isn't consistent with the above spec. That
leads me to believe it might be a 'pre harmonization' amp that was
intended for 220VAC continental Europe use.


And therein lies a problem because harmonization only 'pretends' to
harmonize by inventing a new spec that's simply wide enough to
encompass the existing power systems but it didn't actually change a
blessed thing on the ground. In theory that's 'not a problem' for
*new* designs, which should take into account the extended +-10%
range, but it leads to a perception problem that "we're all on the
same power now so what works in France should work in the U.K." Except
(for the most part) France was and is still 220VAC +-6% while the U.K
was and is still 240VAC +-6% so what was 'once upon a time' built for
220VAC is over voltaged on 240VAC.


All 'harmonization' did was to 'force' manufacturers into making
equipment that works in both 220VAC and 240VAC countries, which they
could and usually did do on their own by either complying with both
specs (one means being transformer taps as Patrick mentioned) or
making models specific to the export region, but, in the process, it
created confusion by pretending something changed. It's also a pain in
the butt for manufacturer's because they can no longer 'fine tune' a
product for the actual mains power as it has to be the mythical, and
wider (more difficult to design for), 'harmonized' voltage of 230VAC
+-10%.


The damn hi-brow makers AND low brow makers SHOULD ensure that users
are made aware of the pitfalls of incorrect mains voltages. But they
all know any mention of anything technical or of any possible negative
outcomes is detrimental to sales figures. They think its better users
burn their gear to bits, with an attitude of utter carelessness about
their customers.


A bit hard to find but ARC actually say something about it, quote:


"Factors which can shorten tube life include inadequate
ventilation, overdriving loudspeakers at continuously high
volume levels, severely fluctuating A.C. line conditions (e.g.
sagging line voltage during summer peaks of air-conditioning
demand), or severe interference pulses or electromagnetic
interference. Power-conditioning products such as line filters,
isolation transformers and the like may or may not help sonic
performance, particularly when used with power amplifiers;
contact your dealer for professional advice. A dedicated 15-amp
or 20-amp A.C. circuit for your power amplifier is the most
effective solution for power-starved audio systems".


[...]


Regards,
Gio- Hide quoted text -


- Show quoted text -- Hide quoted text -


- Show quoted text -


I suspect ARC may have switched to 220V chinese made power trannies.


All I do know is that ppl here buy ARC stuff and don't care about the
mains voltage and then smoke happens.


It is insanely stupid to expect a large heavy box full of very hot
vacuum tubes to last well when the mains voltage is too high, and the
biasing method is so stupid, and there is no active protection if one
or more tubes goes into thermal run-away.


As long as ppl here in Oz understand that there can be problems and
that there are solutions, I have done all I can.


Patrick Turner.- Hide quoted text -


- Show quoted text -


Chances are, ARC may be doing just that ! *US-manufactured
transformers are ver-r-r-y dear these days . And besides, creeping AC
mains voltages are becoming a problem here , as well . What is
historically known as a ' 110 ' volts AC *slowly became 117,
120,125,128 ... I measured what is very close to 130 volts on some
occasions .


I'm not sure where this 'creeping AC' notion comes from but, as I
mentioned to Patrick, I can't find when U.S. power was actually spec'd
at "one ten," despite that being popular nomenclature, and my 1940
Sonora radio declares "117V AC/DC." (doesn't care about 'Hz', which
they would call 'cycles per second', because it's just a single
rectifier off the 'line'.)

With current line voltage being 120VAC a 2.6%, so called, 'creep' over
70 years hardly strikes me as a 'problem', especially since it isn't
really an operational creep as modern tolerances, generally +-5%, are
tighter than in 1940.

What may be the cause of the, so called, 'creep' notion is observing,
as you have done, socket voltage. Reason being, power companies like
to operate on the high side of the range for the obvious reason it's
downhill from there. I.E. You're not going to have more than what's at
the entry and then you have internal line losses. Second, the power
company believes a higher voltage is more efficient because of lower
current, for the same power (disputable), hence lower line losses. At
any rate, with tighter regulation one can operate closer to the
tolerance max (same reason nominal 'crept up' from 117VAC to 120VAC)
but the 120VAC nominal spec hasn't change for many decades.

Point is, simply observing 125VAC on your wall outlet doesn't mean the
'line voltage' spec has 'crept up' as it's still within the 120VAC
nominal +5%.

Having said that those are ANSI specs (C84.1) but utilities are
regulated by your local authority so things 'could' be different in
your locale, as in California where they require tighter regulation,
but local authorities are prone to simply adopt the ANSI standard as
there's little reason to reinvent the wheel (except in California).

ANSI also allows +5.8% under unspecified "short durations or unusual
conditions" for a max of 127VAC. Transients, sags, dips, or swells may
be higher and ANSI specifies that equipment should be able to tolerate
up to +-10% (longer than 10 seconds).

A conservative designer would likely shoot for +-10% continuous, if
you can achieve it without compromising other goals, but SPEC it +-5%
because there's no reason to 'guarantee' more than is required.

(As an original Star Trek fan I call this the "Montgomery Scott Rule:
A good engineer is always a wee bit conservative, at least on paper."

We should probably also note that the undefined quantity "wee bit" is
not a synonym for "arbitrarily large" and doesn't mean "zero sustained
damage from 10,385 direct photon torpedo hits with shields down but,
on paper, we'll spec level 1 hull breach from 2 with shields up.")

A good and serious manufacturer should have built his
equipment with proper VAC input settings in order to accomodate
variations anywhere in the entire world .


That's a wonderful sounding notion but you can't design for "anything
someone might do." You can only design to a SPEC and it isn't
necessarily 'worth it' to sell your product 'everywhere'.

You may also decide to 'regionalize' your products, as in a 'U.S.
model' and an 'E.U. model', instead of trying to make things
'universal' since it might make more sense to use a specific
transformer/power supply rather than incorporate the added expense of
multiple windings/taps, selection switches, and what not, plus the
associated size implications, into every one of them. But, as the
saying goes, "it depends."

Reality has a habit of
biting you . Better safe than sorry !


I could, of course, be wrong but since the unit Patrick mentions is
specifically labeled 220VAC I sort of imagined it might have been
designed and intended for 220VAC. Yeah, I know, silly me.

I sure wish someone would call TUV, UL, CE, et al, and get them to
drop these silly labeling regs because it's blindingly obvious no one
reads them and even when they do they declare it shouldn't matter what
the damn things say anyway. So what's the point? Just leave three
heavy duty wires hanging out the back and let 'em tap into a 10KV
distribution line or clamp them onto a car battery. 'Should work'
regardless, right?


Batteries are great. We still call the plate supply ' B+' ... don't
we ?
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Default Audio Research VM220 and VT200 amps have serious design shortcomings......

On 01/27/11 07:13, Patrick Turner so witilly quipped:
In the Land of the Free aka as Home of the Brave, when the mains
voltage is is off 10--20% we use Variacs . And no need to monkey
around with unnecessary 'modifucations' .


Indeed a variac is one other solution. But to run a pair of VM220 one
would need a variac rated for 1kVA and then if someone turns the
control knob the wrong way......

The mods I'm doing are rather minimal, and easily bypassed, and a heck
of a lot cheaper than buying a suitable variac or well rated 240V:220V
step down tranny


exactly - I also suggested use of a variac, but they're expensive. Some
kind of multi-tap regulator or power conditioner would ALSO work, but
would be prohibitively expensive. The simpler, less expensive solutions
are usually the best.

I also like that voltage reduction transformer idea. A few dollars in
parts, a bit of soldering, and a solution appears. Less shipping cost,
too (lower mass) when you order it on-line.

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Default Audio Research VM220 and VT200 amps have serious design shortcomings......

On 01/28/11 00:53, Patrick Turner so witilly quipped:
snip for brevity,
The vast majority of users are technically illiterate, through no
fault of their own.


Understandably, or else they might attempt to build their OWN amps
instead (from a kit or scratch).

They cannot be blamed for buying ARC and other major "reputable" brand
names of audio gear while thinking they can use it without special
mains arrangements to get reliability if the mains voltage is 13.7%
above the labelled input mains voltage on the unit they buy, ie,
252Vrms instead of the labelled 220Vrms.


I still think that a switching power supply would cost LESS than a power
transformer, _AND_ address the wild fluctuation of supply voltages. You
know, like computer power supplies. They're usually very tolerant, or
at least up to a point. And you could use a single power supply design
for US and AU and UK and everywhere else on the planet. My
manufacturing experience tells me that a 'fits all' component reduces
cost even further by NOT requiring multiple versions of the equipment
(and the component parts) to be ordered, stocked in inventory, and
separately built.

ARC and many other makers in the US and in China etc fail this golden
rule dismally.


They're being cheap in their power supply design (i.e. no taps on the
transformer). That seems a bit strange for something that's "high end".

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Default Audio Research VM220 and VT200 amps have serious design shortcomings......

On 01/29/11 02:40, flipper so witilly quipped:
Well, we can hope no one's listening because if you're not 100% right
on each accusation you're opening yourself up for a defamation
lawsuit.


Its a wonder nobody has sued ARC for causing spinal injuries.


Maybe their intended market is football players and body builders. Or
maybe they offer an accessory crane.


accessory crane. I like that.

it's like 'the old days' when moving a console color TV set was about
like moving a piano.

and you've just given yet ANOTHER reason for the use of a switching
power supply in lieu of a giant hunk of iron and copper windings that
probably costs more, doesn't handle 250VAC power line voltage, and
perhaps weighs too much for one person to move safely without a crane.

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Default Audio Research VM220 and VT200 amps have serious design shortcomings......

On 01/29/11 18:00, flipper so witilly quipped:
Point is, simply observing 125VAC on your wall outlet doesn't mean the
'line voltage' spec has 'crept up' as it's still within the 120VAC
nominal +5%.


if you consider how voltage is regulated, this spec is necessary. Line
voltage is typically regulated by use of a 'motorized transformer tap
switch' that selects different transformer taps (somewhat rapidly) off
of the substation transformer to regulate the line voltage. I would
also expect that line voltage would rise a bit during periods of high
usage in order to compensate for the I^2 * R losses that you get from
the wires running out of the substation into the various destinations,
so that nobody has "too low" of a voltage.

So if you're close to a substation, chances are your voltage is higher
than someone that's remotely located. Does anyone think that THIS might
be the source of the higher than normal voltages in AU? Are the
substations REALLY FAR APART? Longer distance would force the upstream
voltage to be MUCH higher if you want to maintain 'in spec' voltages at
the furthest downstream location.



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Default Audio Research VM220 and VT200 amps have serious design shortcomings......



Snip for brevity,

I mentioned not every hi-fi manufacturer was a crook and then I said
.......
Sometimes perfectly wonderful people can design amps which would
easily withstand one or two serious improvements.


Perhaps but that isn't the topic I've been discussing.


The wonderful people wh have given the world ARC amps could do very
well to improve their products. It is the point I am trying to make,
but I am but a voice in the wilderness......

I managed to complete the servicing on the VT200 this afternoon.


But they have a 27 ohm 1/4 watt plus what appears to be a 1ohm
resistance between the anodes and OPT primary connection. It looks
like an old fashioned carbon comp resistance but may indeed be
inductive, but anyway two had exploded apart from too much heat. I saw
no coil of wire. The other good ones measured 1 ohm.
So during initial testing *measured an average of 67mA of anode
current without the screen current, so maybe the Ia + Ig2 was 75mA and
Pda even higher than I thought it was.


I found that they DON''T have 1 ohm R in the cathode circuits but have
0.2 ohm which are 5 watt rated, well made and none were faulty. Only
one screen resistance had failed. I set the bias by measuring the
voltage across 4 x 0.54 ohm 5W resistors in the anode supplies to each
PP 1/2 of each channel. Bias currents varied by a max of 50% and ther
maximum bias currents determined the final overal setting. Pda is now
less than 20W max per tube.
The tubes were all serviceable. Two which had cooked their series
resistances and one which I found to glow with a red plate all seem OK
and seem stable and happy with the lower bias current.


Glad to hear it.

God only knows why they'd deliberately make it 220VAC, and mark it
220VAC, when everyone 'knows' the harmonized voltage is 230VAC and
their published spec complies with harmonized 230VAC. That is, only
God and you 'knows'.


I don't believe there is any God except the God Of Triodes, and he
sends me a bad electric shock if I ever spout bull****.


I certainly would never want anyone to think I was on a par with some
imagined deity.


I'm just a humble bloke, doin my job, and tryna keep ppl in music
without smoke, noise, and distortion or sullen silence.


My first smoke reduction suggestion would be to match amp to mains, as
in 220VAC isn't 240VAC.


Yes but people don't like to have to spend on having a custom made
transfrormer to achieve what the manufacturer should have provided,
ie, an easy means of matching mains voltage to their product.

All I do know is that ppl here buy ARC stuff and don't care about the
mains voltage and then smoke happens.


Go ahead and tell me how you've done a survey of all ARC amps sold in
Oz and they all have 220VAC markings on them and burned up.


Well, I have at least one colleague who is never surprised with smoke
emanations from ARC amps.


I don't get to see many ARC amps, but those I do see have burned out
parts in them.


And why would they bring you one with no problems? I mean, seriously,
that's like a doctor claiming everyone is sick because that's all he
sees at the hospital all day.


AFAIK, there would be many ARC amps in Oz and which may be teetering
on the edge of their thermal stability.
I'm only one small time audio tech in a small city.
But other people tell me there is an unusually level of heat related
problems in ARC gear.

Some amps get sicker more often than other amps and thus need a
hospital job more often.



The pair of VM220 have a 220Vac sticker. Not very prominent, but there
it is, probably because there are two 110V windings in series.


The question of what a 220VAC amp is doing on 240VAC remains.


Good question. A colleague said ARC has its transformers made by
Magnequest.
Whether that has any relevance is a moot point.
The owner bough the VM220 amps second hand, and from where they came
before he bought them is unknown.
The amps which may have been purchased from China or somewhere with
220V mains.

There is no easy way to reset the mains voltage to suit what we have
here.

This problem is ARC's responsibility IMHO.

ARC should never ever let any amp out the factory gate unless it is
equipped with an easily adjustable mains voltage selector switch, with
selections of 100V, 110V, 120V, 220V , 230V 240V and 250V. This isn't
difficult in such highly priced amplifiers.


Much stuff people don't want elsewhere in the world ends up in Oz
after its has been sold on E-bay.


Well, since that stuff 'from elsewhere' isn't necessarily designed to
operate on 240VAC that's a problem, now, isn't it?


Whatever leaves the ARC factory gate needs to always have easily
adjustable mains voltages for all countries.

I would say much has 110V setting for the USA. Nearly every audiophile
I know has something he bought on E-bay and he has a 240V:110V step
transformer. With preamps it is not critical but with power amps it
only become critical if the mains voltage is too high while ppl ignore
it.


Must be *really* old stuff because my 1940 Sonora radio is rated 117V,
AC/DC.

I can't remember when the US was 110VAC although I can remember it
being *called* "one ten." But that's because people tend to call it
whatever they heard it called so grandpa might have called ...


110V, 115V, 117V, 120V has been used to nominate the USA mains
voltage.

Just what it actually is in any given area is what is really relevant.

Where you havea tube amp with fixed bias, and the Ea rises from say
400V to 450V, and the amp is tetrode, UL, or triode, and Eg2 = Ea,
then at dc operation the anode resistance of 6550 is about 1.2k ohms
at say 45mA of Ia. Pda at 400V would be 400 x 0.045 = 18W. Raising Ea
& Eg2 by +50V will increase Ia by 50 / 1,200 = 41mA. The corresponding
increase in grid bias might be say -47V to -52V and with gm at 0.005A/
V, this Eg1 change reduces Ia by 25mA, but a net 16mA increase of Ia
occurs to give Ia = 61mA, and Pda = 27.5W.
This seems OK for 6550, but where the same grid voltage is used to set
the current in 4 output tubes there may be a a bias current difference
among the 4 tubes of +/- 50%, or from 31mA to 91mA, and then max Pda
could easily be 41W, and I have witnessed one tube with red hot anode
in one of the VT200 monoblocs.
The situtaion is much worse if the initial Ia is set at say 65mA for
where Ea = say 410V with correct mains input voltage.

The VM 220 monos have a screen supply voltage from the same point at
the OPT CT. The screen voltage should be considerably lower than Ea,
say +350V, and be regulated by a SHUNT REGULATOR so that if a tube
malfunctions the extra screen current allows the screen voltage to
sag. The VM220 have their whole speaker secondary winding which is a
match for 16 ohms used as a CFB winding which gives almost identical
operating conditions as a Quad-II amp designed in 1953.
Quad did not bother to regulate either, but there was little need
because they used an Ea of only 350V and had cathode biasing which
tends to make Ra at dc much higher and therefore mains voltage changes
make **** all difference to Ia.

With a regulated screen voltage, the Ra of the 6550 at dc and with an
initial Ia = 45mA becomes about 30k, and hence Ia will change little
with Ea change.
With the addition of non regulated grid voltage bias the change of
bias voltage due to change of mains voltages will further help to
regulate ia and keep Pda of the tubes far more constant than is so far
evident in VM220 and VT200 amplifiers.

Lemme make sure everyone gets the message - ARC amps could be designed
to be far better than they are.

Patrick Turner.
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Default Audio Research VM220 and VT200 amps have serious design shortcomings......

I said....

I suspect ARC may have switched to 220V chinese made power trannies.


All I do know is that ppl here buy ARC stuff and don't care about the
mains voltage and then smoke happens.


It is insanely stupid to expect a large heavy box full of very hot
vacuum tubes to last well when the mains voltage is too high, and the
biasing method is so stupid, and there is no active protection if one
or more tubes goes into thermal run-away.


As long as ppl here in Oz understand that there can be problems and
that there are solutions, I have done all I can.


Patrick Turner.- Hide quoted text -


- Show quoted text -


Chances are, ARC may be doing just that ! *


I have no idea what the real origin may be for ARC trannies. Someone
said Magnequest made them. But Magnequest might have a Chinese
subcontractor who employs another contractor etc who employs sweatshop
labour working for a pittance doing **** that US shareholders won't
allow to be done n the USA.



US-manufactured
transformers are ver-r-r-y dear these days .


Indeed, and if one wants to buy a replacement OPT for an ARC amp,
expect a very high bill.

The bill need be no more than the prices charged by Hammond
Engineering IMHO.


And besides, creeping AC
mains voltages are becoming a problem here , as well . What is
historically known as a ' 110 ' volts AC *slowly became 117,
120,125,128 ... I measured what is very close to 130 volts on some
occasions . A good and serious manufacturer should have built his
equipment with proper VAC input settings in order to accomodate
variations anywhere in the entire world . Reality has a habit of
biting you . Better safe than sorry !-


You have echoed the very point I like to make.

Patrick Turner.
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Default Audio Research VM220 and VT200 amps have serious design shortcomings......

Snip,


With current line voltage being 120VAC a 2.6%, so called, 'creep' over
70 years hardly strikes me as a 'problem', especially since it isn't
really an operational creep as modern tolerances, generally +-5%, are
tighter than in 1940.

What may be the cause of the, so called, 'creep' notion is observing,
as you have done, socket voltage. Reason being, power companies like
to operate on the high side of the range for the obvious reason it's
downhill from there. I.E. You're not going to have more than what's at
the entry and then you have internal line losses. Second, the power
company believes a higher voltage is more efficient because of lower
current, for the same power (disputable), hence lower line losses. At
any rate, with tighter regulation one can operate closer to the
tolerance max (same reason nominal 'crept up' from 117VAC to 120VAC)
but the 120VAC nominal spec hasn't change for many decades.

Point is, simply observing 125VAC on your wall outlet doesn't mean the
'line voltage' spec has 'crept up' as it's still within the 120VAC
nominal +5%.


Having multiple devices connected to the mains and all with diode
rectifiers feeding cap inputs of linear supplies or SMPS dtends to
create a mains wave which is triangular with flat tops, ie, a high 3H
harmonic content.

Power companies are in the business of making profit selling power. So
if they raise Vmains, then mains current increases to the power
consumed tends to increase and the power company profits with no
additional costs to its transmission lines.
Its like water pressure, the higher t is the more ppl use, and up go
profits. To reduce water usage in times of drought and falling dam
levels the comanies have tried reducing water pressure which
significanly reduces water usage. The same idea is not able to be
applied to electricity because a mains drop of say 30% would make many
things fail to function properly including medical and military and
communications stuff.

snip,

A good and serious manufacturer should have built his
equipment with proper VAC input settings in order to accomodate
variations anywhere in the entire world .


That's a wonderful sounding notion but you can't design for "anything
someone might do." You can only design to a SPEC and it isn't
necessarily 'worth it' to sell your product 'everywhere'.


ARC could very easily to accomodate a wide range of mains voltages.

It would be a major improvement to their product which would increase
sales.

Patrick Turner.
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Default Audio Research VM220 and VT200 amps have serious design shortcomings......

On Feb 3, 5:49*am, Big Bad Bob BigBadBob-at-mrp3-
wrote:
On 01/28/11 00:53, Patrick Turner so witilly quipped:

snip for brevity,
The vast majority of users are technically illiterate, through no
fault of their own.


Understandably, or else they might attempt to build their OWN amps
instead (from a kit or scratch).


Most ppl who buy any ARC gear are fairly wealthy.

They usually have no time for DIY.

But after having sold just a few of the transformers I have for sale I
can safely say that manufacturers need never fear loss of sales to
DIYers.
For every 5 who begin to make a hi-fi amp system with tubes and who
buy the transformers, maybe only 1 has got anything at all working
after 5 years.

They cannot be blamed for buying ARC and other major "reputable"

brand
names of audio gear while thinking they can use it without special
mains arrangements to get reliability if the mains voltage is 13.7%
above the labelled input mains voltage on the unit they buy, ie,
252Vrms instead of the labelled 220Vrms.


I still think that a switching power supply would cost LESS than a power
transformer, _AND_ address the wild fluctuation of supply voltages. *You
know, like computer power supplies. *They're usually very tolerant, or
at least up to a point. *And you could use a single power supply design
for US and AU and UK and everywhere else on the planet. *My
manufacturing experience tells me that a 'fits all' component reduces
cost even further by NOT requiring multiple versions of the equipment
(and the component parts) to be ordered, stocked in inventory, and
separately built.


Halcro managed to make SMPS for their 200W solid state class AB mosfet
monoblocs.

Many professional SS amp makers have embraced SMPS.

But making a SMPS capable of +450V at 1amp dc + seems rather too
difficult, and since a tube amp still needs an OPT, weight is high,
and so makers think they may as well include a PT which is the same
weight as the OPT.
May as well get hung for stealing a sheep as for a lamb.


ARC and many other makers in the US and in China etc fail this golden
rule dismally.


They're being cheap in their power supply design (i.e. no taps on the
transformer). *That seems a bit strange for something that's "high end"..


I heard some designers at ARC are young turkeys.......I see the
inconsistency in their design trends.

Patrick Turner.
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Default Audio Research VM220 and VT200 amps have serious design shortcomings......

On Feb 3, 5:58*am, Big Bad Bob BigBadBob-at-mrp3-
wrote:
On 01/29/11 02:40, flipper so witilly quipped:

Well, we can hope no one's listening because if you're not 100% right
on each accusation you're opening yourself up for a defamation
lawsuit.


Its a wonder nobody has sued ARC for causing spinal injuries.


Maybe their intended market is football players and body builders. Or
maybe they offer an accessory crane.


accessory crane. *I like that.

it's like 'the old days' when moving a console color TV set was about
like moving a piano.

and you've just given yet ANOTHER reason for the use of a switching
power supply in lieu of a giant hunk of iron and copper windings that
probably costs more, doesn't handle 250VAC power line voltage, and
perhaps weighs too much for one person to move safely without a crane.


A pair of my 300W monoblocs weighs a total of 100Kg, or 220 lbs.
Each channel has 2 chasiss, one for audio amp and one for PSU and max
weight of each chassis is 25Kg.

So one does not need a crane, forklift, or be a footbrawler who could
easily steal the Statue of Liberty and add it to his backyard garden
area.

Patrick Turner.


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Default Audio Research VM220 and VT200 amps have serious design shortcomings......

On 02/02/11 19:10, Patrick Turner so witilly quipped:
ARC should never ever let any amp out the factory gate unless it is
equipped with an easily adjustable mains voltage selector switch, with
selections of 100V, 110V, 120V, 220V , 230V 240V and 250V. This isn't
difficult in such highly priced amplifiers.


although my transformer experience only extends to things like unwinding
a few burnt ones to see if I could fix them (no) and selecting low
voltage transformers for solid state power supplies "intentionally
overrated" to prevent burnup, I would expect that a properly designed
power supply transformer capable of 110/220 would theoretically NOT be
that much more expensive to make if it contained a few MORE taps, like
120/240 at the very least (if not all of the ones you mentioned). And
yeah, the extra dollar or two for a high end amp should be expected.

But I'm still having a bit of trouble seeing why a transformer power
supply would be superior to a switcher, especially when a switcher would
produce the same output voltages REGARDLESS of the input voltage, and
would most likely cost less, weigh less, etc. (unless large chunks of
iron for the power supply have a nostalgia factor that I"m somehow
missing). Anyway I probably wouldn't be able to convince the amp
makers, but it's an interesting point anyway (I think so).

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Default Audio Research VM220 and VT200 amps have serious design shortcomings......

On 02/02/11 19:44, Patrick Turner so witilly quipped:
Halcro managed to make SMPS for their 200W solid state class AB mosfet
monoblocs.


most likely it was for cost reduction

Many professional SS amp makers have embraced SMPS.


I wouldn't do anything else for a high current power supply.
Transformers are too cost prohibitive. I look at a lot of small
electronic devices (computer related) with 'wall warts' and 5 years ago,
most of them were heavy iron things that fell out of the socket
sometimes. Now they're almost ALL switching supplies, less than 1/3 the
previous size, and weigh practically nothing by comparison. And,
understandably, at a much lower cost per watt.

But making a SMPS capable of +450V at 1amp dc + seems rather too
difficult, and since a tube amp still needs an OPT, weight is high,
and so makers think they may as well include a PT which is the same
weight as the OPT.
May as well get hung for stealing a sheep as for a lamb.


heh, interesting analogy.

Still, a 450V switcher isn't all that difficult. Some of the simplest
switchers perform their regulation from the primary side of the high
frequency toroidal isolation transformer by measuring the rectified
output from the secondary, then use PWM or similar to alter the duty
cycle going into the toroid, with optoisolators and whatnot in the
feedback path to make sure you don't accidentally put 'mains' on the
ground plane. That being said, if the ~450VAC (at xxKhz) output goes
into a simple rectifier and a CLC or LC filter, it wouldn't be a whole
lot more complicated than a transformer [assuming the switcher on the
primary side is a well-known good design]. As I understand it, most
modern switchers use the method I described, particular in computer
supplies. There's a 1990-something US patent describing it all,
actually. I forget who did the patent. Ending point, everything up to
the toroid transformer is pretty much the same for ALL switchers, with
the obvious exception of the expected output voltage and the necessary
component value choices on the secondary side.


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Default Audio Research VM220 and VT200 amps have serious design shortcomings......

On Feb 8, 4:10*am, Big Bad Bob BigBadBob-at-mrp3-
wrote:
On 02/02/11 19:10, Patrick Turner so witilly quipped:

ARC should never ever let any amp out the factory gate unless it is
equipped with an easily adjustable mains voltage selector switch, with
selections of 100V, 110V, 120V, 220V , 230V 240V and 250V. This isn't
difficult in such highly priced amplifiers.


although my transformer experience only extends to things like unwinding
a few burnt ones to see if I could fix them (no) and selecting low
voltage transformers for solid state power supplies "intentionally
overrated" to prevent burnup, I would expect that a properly designed
power supply transformer capable of 110/220 would theoretically NOT be
that much more expensive to make if it contained a few MORE taps, like
120/240 at the very least (if not all of the ones you mentioned). *And
yeah, the extra dollar or two for a high end amp should be expected.


Mains trannies designed by ARC or perhaps Magnequest who may their sub-
contractor are generally sturdy things and can survive having +/- 15%
higher or lower voltages and currents than design centre values.
But the electronics suffers if mains voltages are away from design
centres.

But I'm still having a bit of trouble seeing why a transformer power
supply would be superior to a switcher, especially when a switcher would
produce the same output voltages REGARDLESS of the input voltage, and
would most likely cost less, weigh less, etc. (unless large chunks of
iron for the power supply have a nostalgia factor that I"m somehow
missing). *Anyway I probably wouldn't be able to convince the amp
makers, but it's an interesting point anyway (I think so).


I don't know where a +450Vdc x 1Amp dc regulated SMPS can be found.
Try Googling, and perhaps like me you cannot find anyone building/
using such a PSU and probably you won't find a schematic either.

Many high end professional amps for SS have SMPS with rails of +/-
240V for 5kW amps. One would think 480Vdc is also doable.

But the high end press is always scared of anyone using SMPS because
switching artifacts and high level RF signals get into the audio
signal path or become difficult to supress. But Halcro use SMPS also.
No schematics though.

So SMPS technology has yet to be accepted for high end tube and much
other SS audio amps among fussy buyers.
Its easy to say, just use a SMPS, and in theory its valid, but I am
not going to bash my head against a world which is recalcitrantly
stubborn.
Old fashioned linear PSUs are extremely rugged and unlike my
computer's 300W SMPS, they won't become un-repairable if struck by a
very small amount of lightning. That happened last year and cost me a
new PSU and a MB and later the HD.

Besides people who own ARC or other absurdly heavy expensive amps
don't want a thief running away with one. They want the thief to
struggle, and drop the fukkin amp on his foot, then leave it alone to
limp to a hospital.

Patrick Turner.



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Default Audio Research VM220 and VT200 amps have serious design shortcomings......

On Feb 8, 4:29*am, Big Bad Bob BigBadBob-at-mrp3-
wrote:
On 02/02/11 19:44, Patrick Turner so witilly quipped:

Halcro managed to make SMPS for their 200W solid state class AB mosfet
monoblocs.


most likely it was for cost reduction

Many professional SS amp makers have embraced SMPS.


I wouldn't do anything else for a high current power supply.
Transformers are too cost prohibitive. *I look at a lot of small
electronic devices (computer related) with 'wall warts' and 5 years ago,
most of them were heavy iron things that fell out of the socket
sometimes. *Now they're almost ALL switching supplies, less than 1/3 the
previous size, and weigh practically nothing by comparison. *And,
understandably, at a much lower cost per watt.

But making a SMPS capable of +450V at 1amp dc + seems rather too
difficult, and since a tube amp still needs an OPT, weight is high,
and so makers think they may as well include a PT which is the same
weight as the OPT.
May as well get hung for stealing a sheep as for a lamb.


heh, interesting analogy.

Still, a 450V switcher isn't all that difficult. *Some of the simplest
switchers perform their regulation from the primary side of the high
frequency toroidal isolation transformer by measuring the rectified
output from the secondary, then use PWM or similar to alter the duty
cycle going into the toroid, with optoisolators and whatnot in the
feedback path to make sure you don't accidentally put 'mains' on the
ground plane. *That being said, if the ~450VAC (at xxKhz) output goes
into a simple rectifier and a CLC or LC filter, it wouldn't be a whole
lot more complicated than a transformer [assuming the switcher on the
primary side is a well-known good design]. *As I understand it, most
modern switchers use the method I described, particular in computer
supplies. *There's a 1990-something US patent describing it all,
actually. *I forget who did the patent. *Ending point, everything up to
the toroid transformer is pretty much the same for ALL switchers, with
the obvious exception of the expected output voltage and the necessary
component value choices on the secondary side.


Maybe one day during my next lifetime when I return after re-
incarnation from this life I will R&D a SMPS which is acceptably
rugged and effective and cheap.

Don't hold your breath.

Patrick Turner.
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Default Audio Research VM220 and VT200 amps have serious design shortcomings......

Hi RATs!

A buddy used a SMPS for the filaments of his pre-amp. I never heard
it, but, it was well reviewed

I am not as intrepid. I think voltage doublers are the work of the
Evil One. Sigh. The amp I am now listening to has SS rectification. I
have no pride.

Happy Ears!

Al

PS I used "Jobim" as a keyword for free online music. Possibly even
better than "Wipeout!" Depends on my mood, like the rest of this
planet.

PPS My new PC croaked. I sent it in for free repair. Their repair was
change the MB & HD. Ah, high technology. At least it works again.


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Default Audio Research VM220 and VT200 amps have serious design shortcomings......

On 02/07/11 22:03, Patrick Turner so witilly quipped:
Maybe one day during my next lifetime when I return after re-
incarnation from this life I will R&D a SMPS which is acceptably
rugged and effective and cheap.

Don't hold your breath.


more fun, use tubes

I think that the power pentodes that were used in horizontal flyback
circuits might do well enough. The current ratings are generally high,
even at relatively low plate voltages, and of course they tolerate very
high plate voltages as well. It's sorta needed for a flyback to work.
It also seems like something you'd want for a switching PS. A 'flyback
effect' might even work for the switch, provided that there's an
isolation toroid (similar to solid state switchers). Not sure how many
tubes it would take, but it would be a fun project.
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Default Audio Research VM220 and VT200 amps have serious design shortcomings......

On Feb 13, 7:51*pm, flipper wrote:
On Sun, 13 Feb 2011 00:07:31 -0800, Big Bad Bob





wrote:
On 02/07/11 22:03, Patrick Turner so witilly quipped:
Maybe one day during my next lifetime when I return after re-
incarnation from this life I will R&D a SMPS which is acceptably
rugged and effective and cheap.


Don't hold your breath.


more fun, use tubes


I think that the power pentodes that were used in horizontal flyback
circuits might do well enough. *The current ratings are generally high,
even at relatively low plate voltages, and of course they tolerate very
high plate voltages as well. *It's sorta needed for a flyback to work.
It also seems like something you'd want for a switching PS. *A 'flyback
effect' might even work for the switch, provided that there's an
isolation toroid (similar to solid state switchers). *Not sure how many
tubes it would take, but it would be a fun project.


It's self defeating. To get significant current at low B+ takes
correspondingly higher heater current. On top of that, compared to
modern switchers tubes have astronomically high saturation voltage.
Anything you'd hope to gain would be more than swamped by the added
complexity, size, and power to run it.

The 'tube' version of an SMPS is a vibrator.- Hide quoted text -

- Show quoted text -


Vibator PS were noisy, but allowed a small tranny, and were OK in a
car with vibrator PSU in the boot. But with SS mosfet devices either
ON or OFF, effciency gets high and it seems not so difficult to make a
square wave oscillator which might run silently at 25kHz, maybe no
need to fancy-smancy add on chips and crap one sees in schematics for
most SMPS.

Patrick Turner.
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Default Audio Research VM220 and VT200 amps have serious design shortcomings......

On 02/13/11 00:51, flipper so witilly quipped:
On Sun, 13 Feb 2011 00:07:31 -0800, Big Bad Bob
wrote:


The 'tube' version of an SMPS is a vibrator.


I can see your point about using a vibrator, but there's no regulation
there. ON the other hand, high voltage for color TVs (flyback circuit)
had regulation. Since there's a precedent there, I thought it would be
fun to do the switching PS with the same tubes used in horizontal
flyback transformer drive circuits. But yeah, complexity and all of that.
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Default Audio Research VM220 and VT200 amps have serious design shortcomings......

On 02/13/11 20:39, flipper so witilly quipped:
But with SS mosfet devices either
ON or OFF, effciency gets high and it seems not so difficult to make a
square wave oscillator which might run silently at 25kHz, maybe no
need to fancy-smancy add on chips and crap one sees in schematics for
most SMPS.


The "fancy-smancy add on chips and crap" is there for a reason.


maybe. easiest way to make a switcher is to use an external oscillator,
then a simple voltage comparator driving 'and' gates on the inputs of
the mosfets driving the transformer (usually through an optoisolator).
When voltage is below the desired level, allow signal in. When voltage
crosses the threshold, no signal on the mosfet gates. A similar circuit
could be designed using pentodes and triodes, and for an optoisolator, a
simple neon bulb taped to a photocell with black electrical tape. FYI
Fender did this for their tremolo circuits. Anyway, it's an exercise in
"can it be done" more than "should it be done".


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Dear Mr Turner,
I am looking for a good strong amplifier to drive my Monitor Audio PL 200 loudspeakers. A friend of mine brought me a VT 200 MK 1. It sounds realy superb. However, after reading your article about the design defects of the VT 200 I am worried and I am thinking of not buying it. He is selling it to me for 3000Euros.
It has new valves and it realy sounds superb.
By the way I am using it with unbalanced connection to my preamplifier since it does not have a balanced output. I have connected teh loudspeakers to the 4 ohm on one side and the other in the center posts that it has that are labeled "unbalanced common". Is this correct? I also am not sure how to determine the correct live polarity of the amp since my pre is not very good (an Electrocompaniet Preampliwire 1.3) and when I turn the plug one way(shuko plug), it sounds more detailed but very trebly(if I can say that), on the other side it sounds more quiet and it seems to loose some info. I think that the first should be the right one but perhaps you know of a way for me to find out for sure.
Finaly the big question, (and as I am writing this, I notice that the first two valves at the real left have their bottom parts lighting a brighter than the rest, which worries me, after reading your post, since I do not much about valves, eventhough I am an electronics engineer), should I buy it? Is there somethng I can do to make it more reliable or what do you suggest? Is there another amp that you know that sounds as detailed and as good for (hopefully) less money?
I realy appreciate your opinion, since you seem to have experience with fixing these. Do you think that I can get similar sound with transistor amplifier(suggestions welcome) which is less fussy.
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