Hi all,

Well I'm now planning my first scratch project. And yes it will entail
a substantial learning curve. I want to make PP monoblock poweramps
with preferably 4, but possibly 8 output tubes, and will never use
true pentode mode. I would like to make it switchable between
ultra-linear and triode. Thus I could choose between these 3
reasonably affordable and readily available tubes. I am leaning
towards Svetlana for whichever choice I make.

What could I expect as differences between them? Increased power
output for use in triode mode is a plus but a good damping profile
with lower distortion would be the most critical factor. I am planning
to run them at 450V due to availability and choice of transformers and
also easier to find 450V caps. But if higher voltage is vastly
advantageous in the critical areas mentioned, up to 600V would be
doable I guess.

Thanks,
Wessel

well since there is no such tube as 6556, I guess we can eliminate that one!

(I think you likely are trying to refer to tube type 6550)


cheers!

wild bill
smartass


"Wessel Dirksen" wrote in message
om...
Hi all,

Well I'm now planning my first scratch project. And yes it will entail
a substantial learning curve. I want to make PP monoblock poweramps
with preferably 4, but possibly 8 output tubes, and will never use
true pentode mode. I would like to make it switchable between
ultra-linear and triode. Thus I could choose between these 3
reasonably affordable and readily available tubes. I am leaning
towards Svetlana for whichever choice I make.

What could I expect as differences between them? Increased power
output for use in triode mode is a plus but a good damping profile
with lower distortion would be the most critical factor. I am planning
to run them at 450V due to availability and choice of transformers and
also easier to find 450V caps. But if higher voltage is vastly
advantageous in the critical areas mentioned, up to 600V would be
doable I guess.

Thanks,
Wessel

Let's try to put it in "engineering" form:
1 - Since You are going to make a multi-parallel unit, a large power
handling capability per each tube is not strictly required.
2 - Efficiency could be a "plus", in order to reduce radiated power (HEAT!
OK I live in Italy but You cannot even walk close to a 6S33S in August,
here!)
3 - In order to be used as triodes or pseudo-triodes (UL), these tubes need
to be able to withstand the maximum B+ You're planning to use (450V) which
is a customary value indeed.
From the 1st statement I'd say that EL34s, 6550s or 6L6GC are OK, from the
second I'd prefer the 6L&GC 'cause it needs a lot less power for cathodes
warmup (0.9A instead of 1.6), from the third I'd say the 6550 could have
some problems 'cause it is rated for only 380V on its G2, according to
Svetlana (and GE) data sheets. Nevertheless our fellow RAT mr. Turner uses
the Sovtek 6550 as his workhorse in multi-parallel PP, and I suppose he has
got very good reasons for doing it.
Concluding:
- I tend to prefer the 6L6GC (watch out, personal taste)
- I'd avoid 40+W tubes like KT88/KT90 unless You go down to 4 tubes per
unit and up to some 550V.
- The 6550 could be a good alternative (see above).
- If You are in doubt, provide a filament transformer sized for 1.6A/each
tube and a tapped OPT to handle both EL34s/6L6GCs and 6550s and "live test"
Your monster.
By the way, if You want a B+ about 450V You have to use "stronger"
capacitors, at least 500V, and provide "soft" startup to avoid V surge at
"ignition" (cold tubes-no current-V surge).

Watch out for the WEIGHT of the finished unit, I suppose it will be well
over 50 kgs.


Ciao

Fabio


"Wessel Dirksen" ha scritto nel messaggio
...

"fire bottles" wrote in message
...
well since there is no such tube as 6556, I guess we can eliminate that
one!

(I think you likely are trying to refer to tube type 6550)

Correct 6550. Typo


cheers!

wild bill
smartass


"Wessel Dirksen" wrote in message
om...
Hi all,

Well I'm now planning my first scratch project. And yes it will entail
a substantial learning curve. I want to make PP monoblock poweramps
with preferably 4, but possibly 8 output tubes, and will never use
true pentode mode. I would like to make it switchable between
ultra-linear and triode. Thus I could choose between these 3
reasonably affordable and readily available tubes. I am leaning
towards Svetlana for whichever choice I make.

What could I expect as differences between them? Increased power
output for use in triode mode is a plus but a good damping profile
with lower distortion would be the most critical factor. I am planning
to run them at 450V due to availability and choice of transformers and
also easier to find 450V caps. But if higher voltage is vastly
advantageous in the critical areas mentioned, up to 600V would be
doable I guess.

Thanks,
Wessel

"Fabio Berutti" wrote in message ...
Let's try to put it in "engineering" form:
1 - Since You are going to make a multi-parallel unit, a large power
handling capability per each tube is not strictly required.
2 - Efficiency could be a "plus", in order to reduce radiated power (HEAT!
OK I live in Italy but You cannot even walk close to a 6S33S in August,
here!)
3 - In order to be used as triodes or pseudo-triodes (UL), these tubes need
to be able to withstand the maximum B+ You're planning to use (450V) which
is a customary value indeed.
From the 1st statement I'd say that EL34s, 6550s or 6L6GC are OK, from the
second I'd prefer the 6L&GC 'cause it needs a lot less power for cathodes
warmup (0.9A instead of 1.6), from the third I'd say the 6550 could have
some problems 'cause it is rated for only 380V on its G2, according to
Svetlana (and GE) data sheets. Nevertheless our fellow RAT mr. Turner uses
the Sovtek 6550 as his workhorse in multi-parallel PP, and I suppose he has
got very good reasons for doing it.
Concluding:
- I tend to prefer the 6L6GC (watch out, personal taste)

I'll look into this one as I have no prior knowledge about it. Which
brand is good for 6L6Gc?

- I'd avoid 40+W tubes like KT88/KT90 unless You go down to 4 tubes per
unit and up to some 550V.

In my current first experiment with 4 EL34's, I found the triode mode
to have slightly too little power, and the ultra linear to little
damping. This has prompted me for my first departure from this design,
to either go with 4 higher power tubes, such as KT88, or indeed up to
8 tubes. I have also thought about 6 tubes (3x parallel each balanced
end) which is something I have not heard about or seen before but if I
design it right with the correct transformer parameters etc, I can't
see any reason not to.

Which tube setup from the options above do you feel would provide the
most damping thus allowing a minimum of neg FB and with output power
60W or more.

- The 6550 could be a good alternative (see above).
- If You are in doubt, provide a filament transformer sized for 1.6A/each
tube and a tapped OPT to handle both EL34s/6L6GCs and 6550s and "live test"
Your monster.

Now here's something maybe I don't understand yet. Is the regulation
of the heater filamant current determined by the output capacity of
the transformer? I was under the impression that the internal
resistance of the filament itself provided its own current regulation
so that the transformer for the heaters could be considered a voltage
source.

By the way, if You want a B+ about 450V You have to use "stronger"
capacitors, at least 500V, and provide "soft" startup to avoid V surge at
"ignition" (cold tubes-no current-V surge).

Watch out for the WEIGHT of the finished unit, I suppose it will be well
over 50 kgs.


Ciao

Fabio


Thanks Fabio.

This kind of input from you experienced guys is what forums are all
about and is greatly appreciated.

Wessel

Fabio Berutti wrote:

Let's try to put it in "engineering" form:
1 - Since You are going to make a multi-parallel unit, a large power
handling capability per each tube is not strictly required.

When using tubes in parallel its best to have them not idling with
a huge current, so 1/2 the rated dissipation is usually enough.
This gives you some leeway if one of the 4,6,8 or more tubes decides to run a
bit
hotter than the rest.
But these days 2 x 6550/KT88 will make 50 watts easily as in the schematic at
http://www.turneraudio.com.au/htmlwe...0ulabinteg.htm

But if more power is wanted but with the cheaper 6L6/EL34/6CA7/5881 tubes set
up to run cooler, then use the schematic at
http://www.turneraudio.com.au/htmlwe...0ulabinteg.htm

This last one gives about 100 watts into 4 ohms with the smaller power tubes,
as the web page notes about the circuit say.



2 - Efficiency could be a "plus", in order to reduce radiated power (HEAT!
OK I live in Italy but You cannot even walk close to a 6S33S in August,
here!)

Yes, I know about heat.

One guy has an 8585 amp for the bass speakers, and a pair of SE35 for the rest.

His room gets hot in january.....


3 - In order to be used as triodes or pseudo-triodes (UL), these tubes need
to be able to withstand the maximum B+ You're planning to use (450V) which
is a customary value indeed.

The screen rating of the 6L6 and its cousin, the 807, was 300v.
But with triode or 43% UL, the screen voltage rating is about 450v.
This permits UL operation up to 450v, and that is measured between anode and
cathode.

This is because the volts x current power dissipated is less with triode or UL,

since the signal voltage applied to the screen keeps the dissipation a lot
lower.

I have seen EL34 with 550v running in UL, and triode would also work,
but probably be unreliable for other reason.
And once you start using higher B+ voltages, the amount of class A produced
is a lot less, before the amp starts working class AB.


From the 1st statement I'd say that EL34s, 6550s or 6L6GC are OK, from the
second I'd prefer the 6L&GC 'cause it needs a lot less power for cathodes
warmup (0.9A instead of 1.6), from the third I'd say the 6550 could have
some problems 'cause it is rated for only 380V on its G2, according to
Svetlana (and GE) data sheets. Nevertheless our fellow RAT mr. Turner uses
the Sovtek 6550 as his workhorse in multi-parallel PP, and I suppose he has
got very good reasons for doing it.

The EH 6550 seems to be reliable and rugged for class AB1 amps.
Its one of the best buys around.

I only use anode supply up to about +500v.

In my latest 300 watter versions, the 12 x 6550 output tubes get
20% of the primary signal voltage applied via a tertiary windings,
rather like a gigantic version of a Quad II amp.

The screens are taken directly to a regulated screen supply voltage of +330v,
which is all they need, since the load each tube is high, and the AB1
swing is quite wide enough without hitting grid current.

As the screen voltage is lowered, the anode swing begins to get limited by
the onset of grid current.

With triode and UL using standard available OPTs you have no choice for the
screen voltage;
they must be the same.


Concluding:
- I tend to prefer the 6L6GC (watch out, personal taste)

The GC indicates this version of 6L6 can take the 450v on the screens OK
even in pentode mode.

But if pentode is used, there is no reason why G2 supply could not be lower
than the anode supply.



- I'd avoid 40+W tubes like KT88/KT90 unless You go down to 4 tubes per
unit and up to some 550V.
- The 6550 could be a good alternative (see above).
- If You are in doubt, provide a filament transformer sized for 1.6A/each
tube and a tapped OPT to handle both EL34s/6L6GCs and 6550s and "live test"
Your monster.
By the way, if You want a B+ about 450V You have to use "stronger"
capacitors, at least 500V, and provide "soft" startup to avoid V surge at
"ignition" (cold tubes-no current-V surge).

Watch out for the WEIGHT of the finished unit, I suppose it will be well
over 50 kgs.

My 8585 is 35 Kg. This stereo integrated has 8 x 6550 for two channels,
and a toroidal power tranny, which is 2/3 the weight of an E&I.

The 100 w monos with 6 tubes are about 26 Kg and they have all E&I lams.

Best way to avoid the back aches is to make the amp unit
with its OPT and the power supply as separate units.
One large PSU can be fitted with say 6 octal sockets to allow power to be taken
off
to say 5 normal power channels if HT is to be ever considered, and also a
supply
for a preamp.

The cabling needs careful construction, so that there is a male and female end
arrangement that does not ever allow a the male pins of a plug to
have the B+ on them, so the cables can be soldered into the amp end,
and the male plug goes into the chassis socket at the PS.

Patrick Turner.





Ciao

Fabio

"Wessel Dirksen" ha scritto nel messaggio
...

"fire bottles" wrote in message
...
well since there is no such tube as 6556, I guess we can eliminate that
one!

(I think you likely are trying to refer to tube type 6550)

Correct 6550. Typo


cheers!

wild bill
smartass


"Wessel Dirksen" wrote in message
om...
Hi all,

Well I'm now planning my first scratch project. And yes it will entail
a substantial learning curve. I want to make PP monoblock poweramps
with preferably 4, but possibly 8 output tubes, and will never use
true pentode mode. I would like to make it switchable between
ultra-linear and triode. Thus I could choose between these 3
reasonably affordable and readily available tubes. I am leaning
towards Svetlana for whichever choice I make.

What could I expect as differences between them? Increased power
output for use in triode mode is a plus but a good damping profile
with lower distortion would be the most critical factor. I am planning
to run them at 450V due to availability and choice of transformers and
also easier to find 450V caps. But if higher voltage is vastly
advantageous in the critical areas mentioned, up to 600V would be
doable I guess.

Thanks,
Wessel

Wessel Dirksen wrote:

"Fabio Berutti" wrote in message ...
Let's try to put it in "engineering" form:
1 - Since You are going to make a multi-parallel unit, a large power
handling capability per each tube is not strictly required.
2 - Efficiency could be a "plus", in order to reduce radiated power (HEAT!
OK I live in Italy but You cannot even walk close to a 6S33S in August,
here!)
3 - In order to be used as triodes or pseudo-triodes (UL), these tubes need
to be able to withstand the maximum B+ You're planning to use (450V) which
is a customary value indeed.
From the 1st statement I'd say that EL34s, 6550s or 6L6GC are OK, from the
second I'd prefer the 6L&GC 'cause it needs a lot less power for cathodes
warmup (0.9A instead of 1.6), from the third I'd say the 6550 could have
some problems 'cause it is rated for only 380V on its G2, according to
Svetlana (and GE) data sheets. Nevertheless our fellow RAT mr. Turner uses
the Sovtek 6550 as his workhorse in multi-parallel PP, and I suppose he has
got very good reasons for doing it.
Concluding:
- I tend to prefer the 6L6GC (watch out, personal taste)

I'll look into this one as I have no prior knowledge about it. Which
brand is good for 6L6Gc?

- I'd avoid 40+W tubes like KT88/KT90 unless You go down to 4 tubes per
unit and up to some 550V.

In my current first experiment with 4 EL34's, I found the triode mode
to have slightly too little power, and the ultra linear to little
damping. This has prompted me for my first departure from this design,
to either go with 4 higher power tubes, such as KT88, or indeed up to
8 tubes. I have also thought about 6 tubes (3x parallel each balanced
end) which is something I have not heard about or seen before but if I
design it right with the correct transformer parameters etc, I can't
see any reason not to.

Triode mode with 4 x 6550/KT88 can yield 60 watts class AB1,
even more with class AB2.


Which tube setup from the options above do you feel would provide the
most damping thus allowing a minimum of neg FB and with output power
60W or more.

KT90 will give even more triode power into a lower load value.




- The 6550 could be a good alternative (see above).
- If You are in doubt, provide a filament transformer sized for 1.6A/each
tube and a tapped OPT to handle both EL34s/6L6GCs and 6550s and "live test"
Your monster.

Now here's something maybe I don't understand yet. Is the regulation
of the heater filamant current determined by the output capacity of
the transformer?

Yes. The voltage on the unloaded heater windings is usually set for
6.7v, but when the heaters are all connected, it sags to
about 6.2 to 6.4v, and this voltage will always give the correct
heater current.

If the input tube heaters are run with DC, then the rectifier voltage might be
+12v, and is then resistored down to +6.3v with a dropping resistor,
which also is part of a CRC filter.
Since the AC winding voltage is constant, just the right value of R
is chosen to get the heaters to run at the wanted 6.3v.
Once set up, heater voltages won't change.



I was under the impression that the internal
resistance of the filament itself provided its own current regulation
so that the transformer for the heaters could be considered a voltage
source.

The heaters have a lower resistance when cold than when hot.
But once they warm, they are like resistors, and their current will
vary with applied voltage, as Ohm's law indicates.

but yes, most transformer windings have low output resistance, ie, they
can be considered a voltage source with respect to the loads they have to power.

So a 6.3 volt heater winding might only drop 0.5 volt between no load
and a load of say 3 amps.

Therefore Ro = V change / I change = 0.5 / 3 = 0.16 ohms.

The heaters of 6.3v with 3 amps have their R = 6.3 / 3 = 2.1 ohms.

The load value is over 10 times higher than the power source resistance,
so hence the source is a voltage source.

If however the load resistance was say equal to or lower than the
source resistance, the source is then a current source, since such low value loads will
cause the voltage to wander widely.

For similar reasons triodes are a voltage source, because the
anode resistance is usually 2 to 4 times lower than the load resistance.

Pentodes are a current source, because their plate resistance is
perhaps 5 to 25 times the load value.

UL is in the middle, since the plate resistance is approximately
equal to the load resistance.

This UL to load relationship does indeed not offer enough damping,
since the 1 : 1 ratio means a UL amp has an Ro at the output terminals
of say 8 ohms, and the speaker is 8 ohms only nominally,
but in fact it will be between say 4 and 40 ohms.

So the Ro should be at least 1 ohm, unless we have taken special care to
equalize the speaker Z right across the band and get a flat audio response.
Almost nobody does this, and the speaker makers all expect you to have an
amp with Ro less than 1 ohm so all the filters will work with the right roll off slopes,
and the acoustic response will be flat as long as the voltage level satys put.
The current is allowed to vary wherever it wants to at diferent F.


If you are alergic to NFB, then you are limited to triodes in output stages,
but remember, there *is* an electrostatic feedback loop in all triodes,
but it was put there by the God of Triodes when every triode is born at the factory,
and so let's not argue with a God in charge of lots of volts, OK

Even triodes don;'t give fabulously low Ro.

A pair of KT88 in triode and class A has Ra-a of about 2.2k
If the OPT has a ratio of 10k to 8 ohms,
then you have a 1,250 :1 Z ratio for the OPT, and the
** source resistance is transformed down by the OPT** and when
"looking into" the secondary output terminals, the Ra-a
appears as 2,200 ohms / 1,250 = 1.76 ohms.

To this we must add the transformed DC resistance of the primary winding and the DC resistance of the secondary,
all of which might total 0.8 ohms, so the total Ro = 2.56 ohms.
This is because all winding resistances appear as series R to all windings.
A model of a transformer is a perfect zero resistance winding with an R in series with it.

The only way to get Ro lower is to use more tubes with the same OPT,
or increase the impedance ratio,
both of which drains the wallet to be able to afford the inefficiency,
and even then the Ro can't be lower than the winding R of the OPT.

This is why feedback haters sometimes compromise their principles
to allow say 9 dB of NFB, which is about enough to
halve the Ro of a triode amp, and this reduction of Ro also
includes the effective reduction of the winding resistance, if the FB is taken from the OPT sec to
some preceeding stage before the output stage, usually V1 cathode.

UL needs a minimum of say 14 dB to get to 1ohm,
and pentode amps need about 20 dB.

Patrick Turner.




By the way, if You want a B+ about 450V You have to use "stronger"
capacitors, at least 500V, and provide "soft" startup to avoid V surge at
"ignition" (cold tubes-no current-V surge).

Watch out for the WEIGHT of the finished unit, I suppose it will be well
over 50 kgs.


Ciao

Fabio


Thanks Fabio.

This kind of input from you experienced guys is what forums are all
about and is greatly appreciated.

Wessel

(Wessel Dirksen) wrote in message . com...
"Fabio Berutti" wrote in message ...
Let's try to put it in "engineering" form:
1 - Since You are going to make a multi-parallel unit, a large power
handling capability per each tube is not strictly required.
2 - Efficiency could be a "plus", in order to reduce radiated power (HEAT!
OK I live in Italy but You cannot even walk close to a 6S33S in August,
here!)
3 - In order to be used as triodes or pseudo-triodes (UL), these tubes need
to be able to withstand the maximum B+ You're planning to use (450V) which
is a customary value indeed.
From the 1st statement I'd say that EL34s, 6550s or 6L6GC are OK, from the
second I'd prefer the 6L&GC 'cause it needs a lot less power for cathodes
warmup (0.9A instead of 1.6), from the third I'd say the 6550 could have
some problems 'cause it is rated for only 380V on its G2, according to
Svetlana (and GE) data sheets. Nevertheless our fellow RAT mr. Turner uses
the Sovtek 6550 as his workhorse in multi-parallel PP, and I suppose he has
got very good reasons for doing it.
Concluding:
- I tend to prefer the 6L6GC (watch out, personal taste)

I'll look into this one as I have no prior knowledge about it. Which
brand is good for 6L6Gc?

- I'd avoid 40+W tubes like KT88/KT90 unless You go down to 4 tubes per
unit and up to some 550V.

In my current first experiment with 4 EL34's, I found the triode mode
to have slightly too little power, and the ultra linear to little
damping. This has prompted me for my first departure from this design,
to either go with 4 higher power tubes, such as KT88, or indeed up to
8 tubes. I have also thought about 6 tubes (3x parallel each balanced
end) which is something I have not heard about or seen before but if I
design it right with the correct transformer parameters etc, I can't
see any reason not to.

Which tube setup from the options above do you feel would provide the
most damping thus allowing a minimum of neg FB and with output power
60W or more.

- The 6550 could be a good alternative (see above).
- If You are in doubt, provide a filament transformer sized for 1.6A/each
tube and a tapped OPT to handle both EL34s/6L6GCs and 6550s and "live test"
Your monster.

Now here's something maybe I don't understand yet. Is the regulation
of the heater filamant current determined by the output capacity of
the transformer? I was under the impression that the internal
resistance of the filament itself provided its own current regulation
so that the transformer for the heaters could be considered a voltage
source.

By the way, if You want a B+ about 450V You have to use "stronger"
capacitors, at least 500V, and provide "soft" startup to avoid V surge at
"ignition" (cold tubes-no current-V surge).

The voltage rating of the condensers is B+ times 1,414,
450x1,414=636,39 volts. It is better and easier to use 1,5 times the
B+ to allow for mains change. The rating has to be this value above
the B+ because of the ripple. If 1,5 times the B+ is used, the voltage
rating is 675 volts. To get the voltage, use two condensers in series
with resistors across each of them, for example 100,000 ohm 2 watts
each. I would suggest using a pair of 350 volt condensers in series
which gives a rated voltage of 700 volts. The amount of capacitance is
half the value of the rated mfd of the condenser when in series so a
larger capacitace will be needed. Example, a pair of 330 mfd 350 volt
condensers in series gives 165 mfd at 700 volts.

Those who use voltage ratings just above the B+ in the power supply
are going to replace the condensers faster than if the voltage is
rated right. Using a voltage rating a little above the B+ is fine for
lower level stages because the B+ is filtered. You can use 500 volt
condensers in the lower level stages.


Watch out for the WEIGHT of the finished unit, I suppose it will be well
over 50 kgs.


Ciao

Fabio


Thanks Fabio.

This kind of input from you experienced guys is what forums are all
about and is greatly appreciated.

Wessel

Patrick Turner wrote:

But if more power is wanted but with the cheaper 6L6/EL34/6CA7/5881
tubes set up to run cooler, then use the schematic at
http://www.turneraudio.com.au/htmlwe...0ulabinteg.htm

This last one gives about 100 watts into 4 ohms with the smaller
power tubes, as the web page notes about the circuit say.

Did you mean this?
http://www.turneraudio.com.au/htmlwe...00ulabmono.htm

--
Oskari Heinonen * University of Helsinki * Department of Computer Science
* http://www.cs.Helsinki.FI/Oskari.Heinonen/

Oskari Heinonen wrote:

Patrick Turner wrote:

But if more power is wanted but with the cheaper 6L6/EL34/6CA7/5881
tubes set up to run cooler, then use the schematic at
http://www.turneraudio.com.au/htmlwe...0ulabinteg.htm

This last one gives about 100 watts into 4 ohms with the smaller
power tubes, as the web page notes about the circuit say.

Did you mean this?
http://www.turneraudio.com.au/htmlwe...00ulabmono.htm

Yes indeed Oskari.

I might have got the links wrong.

Sorry to everyone.

And it proves once again not everyone who reads the group is asleep.

Regards,

Patrick Turner.



--
Oskari Heinonen * University of Helsinki * Department of Computer Science
* http://www.cs.Helsinki.FI/Oskari.Heinonen/

Hi Patrick,

The cabling needs careful construction [...]

I considered a single PSU block and two amp blocks
for my current project, but was shocked by the price
of special / professional connectors (AMP, Neutrik, et al)
and cables to transport the needed voltages and currents.

Using the small std European IEC/DIN plugs & sockets (which
would stand the voltages, by the way) seems no good idea
because of chances to confuse them with regular mains
connectors.

What do you use for such connectors/cables, maybe you have
a link at hand?

Tnx2u,

Tom

--
Life: All in all a bad game, but graphics are really good.

Tom Schlangen wrote:

Hi Patrick,

The cabling needs careful construction [...]

I considered a single PSU block and two amp blocks
for my current project, but was shocked by the price
of special / professional connectors (AMP, Neutrik, et al)
and cables to transport the needed voltages and currents.

Using the small std European IEC/DIN plugs & sockets (which
would stand the voltages, by the way) seems no good idea
because of chances to confuse them with regular mains
connectors.

What do you use for such connectors/cables, maybe you have
a link at hand?

Tnx2u,

After a long search for suitable plugs and sockets for my 300 watt amps
I came up with zero which was affordable, and with enough solid pins,
and with
enough distance between pins for the B+, enough current ablity, and also
needing
no special and expensive crimping tools for assembly.

I finished up mounting a pair of normal good quality octal valve sockets

on the chassis.

Then for the plugs I used some phenolic octal plugs from the local Dick
Smith emporium.
These are widely available.
I arranged the pins into pairs triples or quads for the one voltage
using a peice of copper wire slid down the hollow pin so its a snug fit,
and then well soldered.
The cable wires were then brought to the loops of wire and well soldered
and dressed.
So for the heater power, one octal plug was used, so that two lots of 3
pins carry the two
phases of two 12.6 volt AC supplies at 5.4 amps each.
There are 12 output tubes in total. So 6 per each phase of the 12.6v,
with output tubes
set up in 3 paralleled series pairs, so hence 3 x 1.8 amps per 6 output
tubes.
3 octal socket pin joints will handle 5.4 amps easily.
The cables used was mobile crane cable, very flexible, and very tough,
rugged, and well insulated, and colour coded.

Once the plugs were properly fitted to the cable ends, the locating
spigot of the plug
had a steel 4 mm threaded screw inserted, well embeded in epoxy resin.
I used a piece of 30mm dia PVC conduit about 30 mm long to make a tube
to surround the DS plug, and then the voids in the plug were then filled
with epoxy, and once done, there is no access to the
connections, but a cut-it-off and do-it-again isn't expensive.
Movement of the wires at their soldered termination is impossible.

I cut out some plywood panels about 70mm x 70mm with a hole in the
middle
to suit the diameter of the valve base plug and this was screw fixed to
the power supply rear,
so that when the plugs are inserted, the timber blocks stop all yawing
in the
plug by yanking the cables sideways.
They can be pulled out, but not if the force is slightly side on, and
the cables
are so rugged, you can't stretch the wires.
So if the 25 Kg amps fall off a bench, the cables pull out, or they
dangle harmlessly without stuffing the cable.
But sensible folks will always mount such items no more than a foot off
the floor
in a cabinet with no front, and fot of space above and around the amps,
so that
"fall events" simply never happen.

Since there are 16 available pins on the two sockets, there were enough
contacts
to ensure reliable conduction of all currents and voltages, so four
cables
for the two 300 watt monos easily handle the 1,100 watts of power draw
at idle.
The cable for the heaters has 5 x 15 amp rated multi strand wires,
and the cable for the B+, OV, error message, chassis, and one spare
has 5 x 10 amp stranded wires.

Its all pathetically over-engineered, and I don't care, I don't want
anyone ringing me up long distance telling me thay have a poor bloomin
connection
they cannot fix.
And their dog would have to be keen to chew through the cable,
but of course if he does have the teeth of the dinosaur, there is a
little matter of the taste
of 500v to disuade him from the interesting taste of PVC.

I have not seen a more rugged reliable easy to fix scheme anywhere.

Maybe it took a day to connect four plugs, but the milspec equivalent
would have cost me about $1,000, and still had me wondering,
will there be smoke, or will it keep working?
There are special non milspec 450v rated plugs and sockets made for the
cables I am using
and meant for the cranes that have use this cable, but they
are also expensive, and about 75m in dia, and extremely bulky and
ungainly.

Patrick Turner.

"Patrick Turner" wrote in message
...


Tom Schlangen wrote:

Hi Patrick,

The cabling needs careful construction [...]

I considered a single PSU block and two amp blocks
for my current project, but was shocked by the price
of special / professional connectors (AMP, Neutrik, et al)
and cables to transport the needed voltages and currents.

Using the small std European IEC/DIN plugs & sockets (which
would stand the voltages, by the way) seems no good idea
because of chances to confuse them with regular mains
connectors.

What do you use for such connectors/cables, maybe you have
a link at hand?

Tnx2u,

After a long search for suitable plugs and sockets for my 300 watt amps
I came up with zero which was affordable, and with enough solid pins,
and with
enough distance between pins for the B+, enough current ablity, and also
needing
no special and expensive crimping tools for assembly.

I finished up mounting a pair of normal good quality octal valve sockets

on the chassis.

Then for the plugs I used some phenolic octal plugs from the local Dick
Smith emporium.
These are widely available.
I arranged the pins into pairs triples or quads for the one voltage
using a peice of copper wire slid down the hollow pin so its a snug fit,
and then well soldered.
The cable wires were then brought to the loops of wire and well soldered
and dressed.
So for the heater power, one octal plug was used, so that two lots of 3
pins carry the two
phases of two 12.6 volt AC supplies at 5.4 amps each.
There are 12 output tubes in total. So 6 per each phase of the 12.6v,
with output tubes
set up in 3 paralleled series pairs, so hence 3 x 1.8 amps per 6 output
tubes.
3 octal socket pin joints will handle 5.4 amps easily.
The cables used was mobile crane cable, very flexible, and very tough,
rugged, and well insulated, and colour coded.

Once the plugs were properly fitted to the cable ends, the locating
spigot of the plug
had a steel 4 mm threaded screw inserted, well embeded in epoxy resin.
I used a piece of 30mm dia PVC conduit about 30 mm long to make a tube
to surround the DS plug, and then the voids in the plug were then filled
with epoxy, and once done, there is no access to the
connections, but a cut-it-off and do-it-again isn't expensive.
Movement of the wires at their soldered termination is impossible.

I cut out some plywood panels about 70mm x 70mm with a hole in the
middle
to suit the diameter of the valve base plug and this was screw fixed to
the power supply rear,
so that when the plugs are inserted, the timber blocks stop all yawing
in the
plug by yanking the cables sideways.
They can be pulled out, but not if the force is slightly side on, and
the cables
are so rugged, you can't stretch the wires.
So if the 25 Kg amps fall off a bench, the cables pull out, or they
dangle harmlessly without stuffing the cable.
But sensible folks will always mount such items no more than a foot off
the floor
in a cabinet with no front, and fot of space above and around the amps,
so that
"fall events" simply never happen.

Since there are 16 available pins on the two sockets, there were enough
contacts
to ensure reliable conduction of all currents and voltages, so four
cables
for the two 300 watt monos easily handle the 1,100 watts of power draw
at idle.
The cable for the heaters has 5 x 15 amp rated multi strand wires,
and the cable for the B+, OV, error message, chassis, and one spare
has 5 x 10 amp stranded wires.

Its all pathetically over-engineered, and I don't care, I don't want
anyone ringing me up long distance telling me thay have a poor bloomin
connection
they cannot fix.
And their dog would have to be keen to chew through the cable,
but of course if he does have the teeth of the dinosaur, there is a
little matter of the taste
of 500v to disuade him from the interesting taste of PVC.

I have not seen a more rugged reliable easy to fix scheme anywhere.

Maybe it took a day to connect four plugs, but the milspec equivalent
would have cost me about $1,000, and still had me wondering,
will there be smoke, or will it keep working?
There are special non milspec 450v rated plugs and sockets made for the
cables I am using
and meant for the cranes that have use this cable, but they
are also expensive, and about 75m in dia, and extremely bulky and
ungainly.

Patrick Turner.


The Hammond B3 /122Leslie used just a 6pin tube socket to carry 120V and
audio and switching voltages.

couldnt you get away with one Octal socket and plug?
Didnt older amps use this sort of thing for connecting a preamp?
I realize that the voltages may be a bit higher for an amp project but what
are the limits for voltages between pins on an octal socket?

Doug