This amp consists of 3 stages. All of them determine the distortion characteristics of the amp.
A (big) difference between the distortion produced by each channel, destroys or at least distorts the imaging.
2 out of 3 stages are determined by the driver/phasesplitter section around the 6N1.
The first stage already has a rather low anode-cathode voltage, so even smaller differences
between tubes will create a different opearing point. Different operating point means
different distortion spectrum.
That's the reason why I want those 6N1P's (or equivalents) to be matched.
In this case, they don't have to be internally balanced, but matched between tubes.
To a lesser extent, the same thing goes for power tubes.
But a matched quad is not more expensive than two matched pairs...
So why would I buy two pairs?
btw, I found nothing bad on the stock chinese 6P15's, they were properly matched (or it was just my lucky day).
The chinese 6N1P's were far worse! (badly constructed and totally different from each other) Replaced them with Siemens E88CC - yes, matched pair.
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The keyword is (big)
How big is the difference if output pairs are not matched? Is it audible at all?
This is the question.
Thing is, I don't know what the maximum allowed mismatch between channels is.
(maybe it's bigger than I assume now)
But if you bias one channel slightly hot and on slightly cold (changing cathode resistors), the effect is clearly audible.
- male voices crawl to the hot channel, female voices to the cold -
If I'm correct, open loop gain is around 21, closed loop gain around 8.
That's -8.4dB.
Why the question?
How big will be the difference in gain if tube pairs are unmatched when this feedback is applied?
Wow, I overlooked the 200V limit of g2.
This means that the Suppo Golden Voice, supplied with Chinese 6P15 tubes is actually wired in "self destruct" mode. (original schematic)
Only peepz with JJ EL84's are safe.
I pretty much do NOT understand anything on page 31 tubesteve's post (#308) and oneyedk's post(#310).
oneyedk, what all this means? (tubesteve's and your post). I don't understand any technical discussions. Can you do an outline in simple understandable language for people like me? Is Suppo golden voice with 6P15 tubes bound to die after short service duration? So does this mean only safe tube choice is the JJ EL84's?
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Euhm... There will be no difference in gain...
Problem is not the difference in gain, but the difference in "colour" between channels.
On paper, the only safe choice is JJ EL84.
(JJ EL84 is the best current production EL84 on the market, available at a fair price)
In practice, the stock 6P15's of the suppo seem to survive the theoretical abuse. Mine are still triode strapped without lowering g2 voltage.
If they would die a little early, it's not a big deal, they don't cost an arm or a leg (if you stay with 6P15-EV's or JJ EL84)
The impression I got was that using 6P15 meant shorter life for the amplifier itself. That's really not the case right?
Difficult to answer that question...
Nobody knows how much these particular 6P15's can take, mine show no signs of decay after about 6 months of use (or abuse, if you like).
The people at Suppo are very helpful and friendly, so if you run the amp with stock tubes and it fails after a short while, I'm sure they will help.
On the other hand, this amp is fairly simple, so if a failing tube would take out some components, they are replaceable.
we don't choose tube amps for their reliability, nor do we read and post on DIYaudio to leave amps as they were Running Hot and Sweet
Hello Suppo owners,
I've been running my modded amp 5 hours a day every day for the past 4 months and I've not experienced any problems so far. The amp runs extremely hot, but it still sounds so sweet. I still haven't modified it for triode mode, but I think it's about time.
Regards,
David
Hello Suppo owners,
I've been running my modded amp 5 hours a day every day for the past 4 months and I've not experienced any problems so far. The amp runs extremely hot, but it still sounds so sweet. I still haven't modified it for triode mode, but I think it's about time.
Regards,
David
Thanks all,
We will redesign this machine later. sure will have the tubes shown, earphone socket, and more improvmnet. It will be a different machine but yes, better sound.
We keep building large powerful EL34 in the past few months because people say the EL34 is a bit thin. so we need more power: mono block EL34*8 each channel 75W power. So far anyone heard these mono block can say nothing. simply because they have never thought that music can be sound like that.
I wonder anyone would like to take it a try. We will offer a very special price again for those who would like to try, DIYers only. I believe you will be supprised again.
We will redesign this machine later. sure will have the tubes shown, earphone socket, and more improvmnet. It will be a different machine but yes, better sound.
We keep building large powerful EL34 in the past few months because people say the EL34 is a bit thin. so we need more power: mono block EL34*8 each channel 75W power. So far anyone heard these mono block can say nothing. simply because they have never thought that music can be sound like that.
I wonder anyone would like to take it a try. We will offer a very special price again for those who would like to try, DIYers only. I believe you will be supprised again.
guys, please keep in mind, efficiency is an increasing point of environmental iprotectional issue: 75W per channel with 4 or 8 pcs. of el 34 is soon no more a topic. and: who needs this power with good efficient speakers in his home?.. please think again. next: statement EL34 sounds thin: never heard this. what means thin?. what means thin in engineering understanding, this doesnt exist there. data/ values/ dB/ listening room/ speakers used/ etc. are missing. its too personal. powerful musical noise isn't all
Tube Amp Doctor Verstärker Röhren - Tubes and Amp Kits
JJ (former Tesla) EL84
6N1P (category Tubes: odd ball)
Those should do fine...
Another option is to buy some Russian 6P15's an 6N1P-EV's on ebay,
but I like TAD, they have fair prices and good customer support...
Did you drop the amp???
JJ (former Tesla) EL84
6N1P (category Tubes: odd ball)
Those should do fine...
Another option is to buy some Russian 6P15's an 6N1P-EV's on ebay,
but I like TAD, they have fair prices and good customer support...
Did you drop the amp???
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Could you measure the voltage on pin 6 (or 2) of that 6CG7 tube please?
It may sound ok, but around 60V anode for that triode is a bit low to my taste.
With a fine 6N1P, voltages are:
Vb: 246V
Pin 1 : 166V
Pin 2/6 : 77,7V
Pin 3 : 79,5V
With the stock resistor values...
Better safe than sorry, best read Georges excellent guide before entering the high voltage zone that every tube amp is.
Electrical Safety
Everything unplugged...
I put the amp upside down on the edge of my desk.
Resting on it's transformer. Tubes "hang" over the edge...
(the transformers are heavy enough to keep the amp in safe balance)
Remove the bottom cover.
First connect the speakers again.
Then connect the negative connector of your voltmeter (black probe) to the amp's ground, I clipped it to one of the black speaker posts.
Make sure you meter in on and switched to Volts DC.
Plugin the amp and switch it on.
Wait 2 minutes before you start measuring, let tube temperature and voltages become stable for a while.
Put one hand on your back.
Now you can take the red probe of your multimeter and start poking around (with the free hand), make sure you touch only one pin at a time (we don't want to scare ourselves or destroy the amp).
Prepare for a slight "hum" or "buzz" in the speakers when you touch a tube pin with the red probe. This is perfectly normal, but you better know this in advance.
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