[jh]

Eeyore schrieb:

jh wrote:


Eeyore schrieb:

I'm a pro-audio designer with 35 yrs experience in the business and have plenty of knowledge of tube circuitry and

I even played a part in getting one tube guitar amp into volume production.

Hí,
just curious,

which guitar amp?


http://www.studiomaster.com/hp3.html

Graham


Hi Graham,
very interesting, i´ve never seen one of them in real life, althoug i
think i remember some ads years ago. Competitor to burman and boogie
propably.

Thank you

Jochen

[Eeyore]

jh wrote:

Eeyore schrieb:
jh wrote:
Eeyore schrieb:

I'm a pro-audio designer with 35 yrs experience in the business and have plenty of knowledge of tube circuitry and

I even played a part in getting one tube guitar amp into volume production.

Hí,
just curious,

which guitar amp?


http://www.studiomaster.com/hp3.html


Hi Graham,
very interesting, i´ve never seen one of them in real life, althoug i
think i remember some ads years ago. Competitor to burman and boogie
propably.

Exactly so.

Owners tend to hang on to them I'm told.

Graham

[Patrick Turner]

Phil Allison wrote:

"Patrick Turner"
Phil Allison wrote:


** Plenty of reliable BJT SS guitar and hi-fi amps have no such diodes.

( MOSFETS have such reverse diodes inherent inside the device.)

The need for "flyback diodes" only arises when the particular BJT amp
incorporates VI limiting circuitry to protect output devices from over
dissipation and SOA induced failures.

See: http://sound.westhost.com/vi.htm


Your article at the above address goes a long way twoards explaining the
pitfalls of BJt and mosfet use and VI limiting.

** Barely a beginner's primer - in fact.

Like most seemingly simple things - it soon gets all complicated when you
look right into it.

UK songwriter, Pete Townshend , said it all over 40 years ago.

In a little tune called "Substitute".

No allusions to BJTs intended.....

Rod Elliot explains further.....

** Well, he had to use his " editor's discretion " - didn't he ?.


Well, I guess he has that perogative, only avoided if you set up
your own website, and then you are your own editor, which means you must
mock your own efforts
at least privately before publishing them, and tailor your utterings to
be moderately plausible
at least, lest the knockers out there reduce one to a laughing
stock.....
We should permit them a smile or two, but not to have them
laugh all day at us, and never forgive us.

But methinks I'll stick to using clamping diodes where I see fit, and
stay clear of using bjts
in output stages of SS amps; I much prefer mosfets.

I also don't specialize in designing musician's amps, and folks I make
amps for
never go near clipping, so little smoke comes from my designs.

If one is ever doubtful about the output stage of any amp to withstand
signal voltage overdrive when loaded or not loaded, they could try
arrangeing voltage limiting at the input using a pair of
biased diodes so that the input is clipped just before the output clips
when loaded by the rated load.

One must always assume some clown won't have a speaker connected, and
that
he will turn up the volume to try vainly to get some sound....


Patrick Turner.


...... Phil

[Patrick Turner]

Eeyore wrote:

jh wrote:

Eeyore schrieb:
jh wrote:
Eeyore schrieb:

I'm a pro-audio designer with 35 yrs experience in the business and have plenty of knowledge of tube circuitry and

I even played a part in getting one tube guitar amp into volume production.

Hí,
just curious,

which guitar amp?


http://www.studiomaster.com/hp3.html


Hi Graham,
very interesting, i´ve never seen one of them in real life, althoug i
think i remember some ads years ago. Competitor to burman and boogie
propably.

Exactly so.

Owners tend to hang on to them I'm told.

Graham

It reminds me of an Ampeg I have here for a check up.
Its full of power mosfets with a fan, and lots of
signal level vacuum tubes...

Patrick Turner.

[Alan Rutlidge]

"Patrick Turner" wrote in message
...


Lord Valve wrote:

Chris Hornbeck wrote:

Despite what you may have seen from a loud-mouthed
know-it-all on this NG, don't worry.

Well, ****-fire and boy howdy, son...

You're wrong, but you can derive some small solace
from the fact that you're wrong for all the right reasons,
chief among them being ignorance regarding actual
field operating conditions for *guitar* amplifiers.

You've also never seen an Epiphone Valve Junior,
nor the schematic thereto. Right?

So - this amp runs a single EL84, giving an output
of around 4 watts RMS. One 12AX7. SS bridge
rectifier for the HV, as well as one for the heaters.
No screen resistor. The entire shebang - including
the speaker - *retails* for $139, and can often be
had for less than $100, brand new in the box. In
short, it's a cheap-ass piece of Chinese ****,
a bare-bones minimum design intended to sell
for the lowest price possible - less, in fact, than
most audiophools spend on a couple of snob-glass
preamp tubes.

Think any corners were cut?

I've had around a half-dozen of these across my
bench in the last year. All but one had the same
problem: fried socket. Cause: "I hooked it up
to my (brand XYZ) speaker cabinet cuz it wasn't
loud enough for me to play with a drummer."
Said speaker cabinet, of course, was nearly
always an 8-ohm box. One was 16.

This is a 4-watt amp commonly purchased by
the worst gear abusers on the planet: guitar
pickers. Since it's only 4 watts, it is *always*
played at full-bore output clipping, for max
distortion and "blues tone." Its (often short)
life is one of maximum stress, placed upon
the sleaziest components imaginable.

Now, son - you may know what you may
know, and it may well be at odds with what
I've said, but I have hands-on time with this
particular gizmo, and I know for certain it
eats tube sockets when operated into a
higher than spec load. If you want to show
me the math which proves that a bumblebee
can't fly, be my guest. I've seen 'em fly, so
I'll take your "knowledge" with a grain of salt,
if that's OK with you. You don't catch my ass
on this NG telling the audiophools about their
SET 300B snob designs for a fairly good
reason: I know jack **** about 'em. The
difference between me and the audio******s
is that I can admit it.

Lord Valve
Expert Guitar Amp Dude


Lordy Lord. I agree mostly.

But the failures when speakers are changed from 8 to 16 ohms isn't
why it fails; failures due to arcing is gonna happen anyway
since a speaker presents a high Z at each siode of its power range, and
chinese crapologists dunno how to make good ****.

And the chinese dunno what they are doing except they try to copy ****
and
finish up with ****tier **** that you can poke a stick at.....

They make 'Goochi' handbags for sheilas, 'Rolecks' watches for the
un-wary,
and any ****en thing goes as long as some poor ******* buys it.

Patrick Turner.

I have to agree with you. Unlike the Japanese, the Chinese copiers are not
very good at copying technology and getting it right.
Sure there are exceptions to the rule, but by in large most Chinese audio
gear is crap. Cosmetically it may look acceptable but under the skin there
is a lot of technically compromised "design", demonstrating a fundamental
misunderstanding of electronic engineering principles.

And yes you are correct in so much as whilst there are fools who will buy
this crap, they will continue to manufacture it. Just goes to prove that 50
years of communism didn't kill off the capitalist ideology of making a quick
buck.

Cheers,
Alan

[Patrick Turner]

Alan Rutlidge wrote:

"Patrick Turner" wrote in message
...


Lord Valve wrote:

Chris Hornbeck wrote:

Despite what you may have seen from a loud-mouthed
know-it-all on this NG, don't worry.

Well, ****-fire and boy howdy, son...

You're wrong, but you can derive some small solace
from the fact that you're wrong for all the right reasons,
chief among them being ignorance regarding actual
field operating conditions for *guitar* amplifiers.

You've also never seen an Epiphone Valve Junior,
nor the schematic thereto. Right?

So - this amp runs a single EL84, giving an output
of around 4 watts RMS. One 12AX7. SS bridge
rectifier for the HV, as well as one for the heaters.
No screen resistor. The entire shebang - including
the speaker - *retails* for $139, and can often be
had for less than $100, brand new in the box. In
short, it's a cheap-ass piece of Chinese ****,
a bare-bones minimum design intended to sell
for the lowest price possible - less, in fact, than
most audiophools spend on a couple of snob-glass
preamp tubes.

Think any corners were cut?

I've had around a half-dozen of these across my
bench in the last year. All but one had the same
problem: fried socket. Cause: "I hooked it up
to my (brand XYZ) speaker cabinet cuz it wasn't
loud enough for me to play with a drummer."
Said speaker cabinet, of course, was nearly
always an 8-ohm box. One was 16.

This is a 4-watt amp commonly purchased by
the worst gear abusers on the planet: guitar
pickers. Since it's only 4 watts, it is *always*
played at full-bore output clipping, for max
distortion and "blues tone." Its (often short)
life is one of maximum stress, placed upon
the sleaziest components imaginable.

Now, son - you may know what you may
know, and it may well be at odds with what
I've said, but I have hands-on time with this
particular gizmo, and I know for certain it
eats tube sockets when operated into a
higher than spec load. If you want to show
me the math which proves that a bumblebee
can't fly, be my guest. I've seen 'em fly, so
I'll take your "knowledge" with a grain of salt,
if that's OK with you. You don't catch my ass
on this NG telling the audiophools about their
SET 300B snob designs for a fairly good
reason: I know jack **** about 'em. The
difference between me and the audio******s
is that I can admit it.

Lord Valve
Expert Guitar Amp Dude


Lordy Lord. I agree mostly.

But the failures when speakers are changed from 8 to 16 ohms isn't
why it fails; failures due to arcing is gonna happen anyway
since a speaker presents a high Z at each siode of its power range, and
chinese crapologists dunno how to make good ****.

And the chinese dunno what they are doing except they try to copy ****
and
finish up with ****tier **** that you can poke a stick at.....

They make 'Goochi' handbags for sheilas, 'Rolecks' watches for the
un-wary,
and any ****en thing goes as long as some poor ******* buys it.

Patrick Turner.

I have to agree with you. Unlike the Japanese, the Chinese copiers are not
very good at copying technology and getting it right.
Sure there are exceptions to the rule, but by in large most Chinese audio
gear is crap. Cosmetically it may look acceptable but under the skin there
is a lot of technically compromised "design", demonstrating a fundamental
misunderstanding of electronic engineering principles.

And yes you are correct in so much as whilst there are fools who will buy
this crap, they will continue to manufacture it. Just goes to prove that 50
years of communism didn't kill off the capitalist ideology of making a quick
buck.

Cheers,
Alan

Just place yourself in the position of a poor chinese person
working his guts out in a miserable life in china
and he hears that a Jolida with 4 KT88 and giving 60 watts per channel
sells for
around usd $3,000 to western nation buyers, but he only gets usd $32 to
make the whole caboodle.

Something is SERIOUSLY wrong with a production system whereby the worker
gets ripped off
so badly that there is a 40 dB difference in worker reward and product
endprice with all these
cowboys between the worker and buyer producing absolutely nothing except
a pain in everyone's arse.

Unfortunately, democracy endorces hyprocrisy, and allows the chinese
worker to be well and truly ripped
while Mr BIg Arse Westener has it easy.

Placing tarriffs on imports won't change the situation, but a good blood
letting revolution in China
might, but then out of nowhere will come mandarins who will squash the
worker
without mercy.

But things are slowly changing and now one can buy about the same amount
of Jolida tubed horsepower
from a *lousy quality* company in HK, presumably called "hi-fi amp"
because that's about all the
information one gets with their amp; its screen printed on the front of
the amp
on the black powder coated metal. It does about the same thing as the
Jolida, but costing
only usd $400 and available direct via the INTERNET!!!, and including
freight I was told.
Intelligent Chinese workers whose minds have not been tricked by the
persuasion of the
silly old communist ruling system and whose minds are not rotted by
drudgery,
misspent youth, and poor diets must be rejoicing that finally they can
get something to and from
western countries without all the mainly western country roundeye
arsoles whacking the price up.

There is no after sales service, and the amp tends to blow up after a
week or two
because of the attrocious quality and short longevity of the very nice
looking KT88,
made in China in god knows what conditions.
I've had two such amps in the last 3 mths come to me for "revisions".
The first i converted to triode which was a minimum amount of circuit
work, the second
I just ripped out all the wiring and its now a TURNER with all the usual
benefits of my
circuitry.

You are dead right when you say
"Cosmetically it may look acceptable but under the skin there
is a lot of technically compromised "design", demonstrating a fundamental
misunderstanding of electronic engineering principles."

I was not able to apply a great deal of NFB because the OPTs are no
better than the
crappiest crap that was the majority of production in western contries
in 1955,
and an example is the Leak Pt 1 which was difficult to stabilise
unconditionally.
In Oz, in 1955, very lousy crappy inadequate poor quality were sold by
Fergesson of Sydney, and
A&R of Melbourne. Both companies produced a range of quality OPTs,
low-fi, medium-fi, and hi-fi,
and the low quality was the best seller because Joe Public is usally a
financially embarrassed
silly miserly short-sighted dude who does not know quality even when it
bites him on his arse.

However, after some considerable farnarcling around I was able to get
this latest Chinese amp
to give 30+ watts with a lot of class A in 25% UL, and get the Rout to
be less than 1 ohm,
and get thd /imd way lower than originally. Bandwidth is 50kHz with a
good bass response, and
without the artificial deliberate boost of bass F of the original.
I have fitted Sovtek KT88, but almost anything other than Chinese KT88
will be an improvement.

I thought they'd got over their poor reputation problem for KT88, but
obviously not.

I abolished the use of a shared cathode R and single bypass electro as
this
biasing technique tends to make thermal runaway after bias current
imbalance
drift occur much more likely. In Quad II, there is also a single lousy
180 ohm common biasing R to the two KT66 cathodes between the OPT CFB
winding CT and 0V.
This 1955 arrangement has meant many more KT66 wore out sooner rather
than later because
if one tube decides to conduct a bit more current than its mate, then
the Ek rises, tending to cut off the current in the lesser currented
tube.
When serviceing Quad II amps its common for me to find one KT66 with
30mA,
and the other with 90mA, and the hot one has a red spot on its anode,
and the music is distorted at anything above a whisper of sound.
When a separate pair of 470 ohm R plus 1,000 uF caps are employed to
bias these very
imbalanced tubes, the bias of each is much closer, and usally within 5%
of having ther same Idcq.
Even Leak knew about all this which is why they didn't avoid using the
two bias R and two bypass caps.

Now when the stupid Chinese decide to copy the sestern bull**** of the
1950s without
making well matched output tubes that at least stay matched for awhile
like the
usaully better quality NOS productions of KT66 ijn the west, one can
expect
real trouble soon.
I have seen the Chinese amp burn out the aluminium clad 25 watt 400 ohm
common
cathode resistance. Trouble is, when the Chinese mounted the resistor,
its
10mm away from the chassis and floating at the end of two 25mm x 3mm
bolts, so the heat of the R isn't
able to be dissipated to the chassis let alone a heatsink, so the
Pd rating for the R is effectively reduced very muchly.

The Chinese amp starts life being made as a one chassis fits all
occasions,
and a SECOND cover chassis is fixed down over the top of the first.

This is an act of SUPREME ORIENTAL CRAPOLOGY!!!
If not crapology, then ****wittery may be more easily translated for the
chinese to read.

There are numerous screws and bolts that CANNOT BE ACCESSED DURING
SERVICING
and the only way to replace some parts is by the most protracted time
spent
arguing with Chinese metal work with the aid of a small angle grinder.

Needless to say the quality of the volume control pot is quite lousy,
and it is not even a log
scale, but a linear one, probably because they'd not be able to get good
balance with a log scale
pot.

These "El Cheapo" amps from china also are riddled with unnessary
gimicks.

This integrated amp I have lately worked on has two "magic eyes" which
appear
to be Chinese developed tubes because I cannot find any data for the
numbers on the glass.
But who needs to know the dancing pale green light indicating the output
level up
to -6dB where the indicator runs out of headroom, and fails to indicate
clipping.

Then there are no fewer than 3 tube twin diodes, but they are all
paralleled
to add to the nightime tubic visual impression, and used as a series
single diode.
Its an amp that is supposed to be twin monobloc, but there is only ONE
B+ supply,
derived by means of silicon bridge, and lots of 220uF caps in series. A
single 0.5 Henry
choke aids in filtering the B+ with CLC, and is better than nothing but
it is
very paltry choke offering indeed, and further illustrates the
parsimonius attitude of the muddle headed designers.

There is probably more I could bring to everyone's notice,
but until the Chinese try a LOT harder, I will continue to believe
believe they
just make cheap garbage that looks nice.

But at least they wil sustain singling lessons after treatment with hot
sodering
irn and long nose pliers; all these sickly specimens brighten up
when forced.

Meanwhile, the western country rip off merchants will continue to try
to charge the price the market will bear without the slightest concern
about the
cost of production, except to try to force it to be as low as inhumanely
possible.

We have just seen the Oz brand Blundstone, a maker of fine workboots
secumb
to the fickle tastes of Oz workers who were failing to buy the product
in such large numbers,
probably because hard work is now not being done as often, and punk
rocker dress styles are passe'.
They just sacked 300 Oz workers, and announced that asian labour would
be used for
future production. This makes sure the shareholders get the same profit
per pair of boots sold,
and the company directors/owners still do OK, but **** everyone else who
makes boots in Oz.
The boot price can be kept low to compete with cheap asian imports made
by
ppl working 6 day weeks of 12 hrs per day for $2 per day, and with no
conditions like
health insurance or long service leave, superannuation etc.

Still, for the asian workers, its better than selling bags of chicken
manure to each other in the villages.

Some would say the best thing for the price of bananas in Oz is to close
down all the
Oz banana growers and pack them off overseas on a permanent long
holiday,
then just import all tha bananas from the Phillipines, a country whose
entrepreneurs desperately want to do to get onto Mr Western Country
Dollar,
and the only thing holding them back are Australia's rigorous quarantine
laws.

We wish to continue to have local secure production of disease free
fruit.

But oh how the business arsoles hate this government intervention!
They think we should have the same lot of food crop diseases everyone
else has,
and that'd make it a level playing field, and really, it is amazing
lots of these AHs have not managed to sneak diseases into OZ.

So Globilization stumbles along, creating losers and winners along the
way,
and someone said I should get my amps made in China.
I replied that I didn't want to convert my career into
one where I became a "**** MERCHANT".

I've kept an eye open for over 6 years for decent quality OPT and power
trannies that don't hum badly
but I ain't seen any yet.

Maybe we will see the Chinese become leaders not followers in many
fields of endeavour,
rather like we witnessed Japan rise from the ashes of WW2 to become a
favourite
manufacturer if we look at what Toyota and Canon and Sony have achieved.

But I ain't holding my breath, I see that world changing conditions are
different to
post WW2 asia, and the Chinese are very different to the Japanese, with
a different history.
And developing ethics acceptable to the West is very difficult for the
Chinese;
they had a BIG CHIEF ARSOLE called Mao who murdered millions to upgrade
Chinese world status, and his decendant functioneries still don't wanna
lose their
powers, but I guess they too must all die some day.
Things could then get worse.

What happens when a large country like China which just demonstrated it
can shoot
down small satellites with a well aimed rocket gets a mind to "expand
its sphere of influence"?

I think dumb folks build tube amps there, but the bright guys are
employed elsewhere.


Patrick Turner.