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Russian NOS tubes harsh, ragged.

GuyNoir

GuyNoir

Hallowed State
Hello:

I have a Chinese Push-Pull amp with four Chinese 6P1T power tubes, functionally equivalent to EL84, and two GE 5670 driver tubes. The amp is new to me, so I decided to start with fresh tubes. I got a quad of matched 6P1P-EV Russian tubes, which are gold pinned military grade 6P1T tubes. I also picked up another pair of matched NOS JAN GE 5670 drivers. I have probably 20-25 hours on them. My initial impression was that with the new tubes, the sound had changed for the worse. Decidely harsh. I chalked it up to my imagination, because these Russian military tubes are supposed to be the *hit.

But while listening last night, I noticed a certain musical passage that was undeniably grainy and course. I put the old tubes back in it, and now it's as smooth as silk. I have no way of measuring the new Russian tubes, but they all have a subtle light blue florescence (not gaseous) deep within the tube, which I've read is an indicator of a healthy new tube.

Do I need more burn-in time before making an assement? Or may I conclude that the Chinese tubes are better in this application? I haven't considered that the 5670's could be the issue - I suppose I could try the Russian tubes with the old GE 5670 as a process of elimination.

What say you?
 
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The front end tubes will make the really big difference. I'd concentrate my efforts there, and leave the Rusky power tubes in for awhile.
 
What jaymanaa said...plus

try both tests of old drivers/new outputs and new drivers/old outputs and see if something stands out.
 
I'm pretty impressed with the sonix and value in the surplus Russky 6L6s. Clean, fast, and musical.

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The older GE JAN 5670s are definitely smoother than the new ones, though now, I'm not hearing what I heard last night. Who knows; maybe the amp wasn't warm, the tubes weren't seated correctly, or there's a loose nut at the wheel?

In my price range, I have a line on either a matched NOS pair of 1960 GE five star 5670, or an NOS matched pair of RCA "Command" 5670. According to one tube roller, the RCA, with its "extra support post" is better than the GE five star. I'm looking for something just a tad mellower.

Does anyone have any experience or opinions with these?


Pio1980:

Thinking of a Musical Paradise MP301 MkIII deluxe msyelf. I'll keep that in mind!
 
A quad of NOS Russian 6v6 came with a Maggie 8804 that I bought from a local AKer. He bought them as back ups to the original tubes that came with the amp so he had barely used them. Same as these: http://m.ebay.com/itm/201132599345?nav=SEARCH. They sounded grainy and disappointing too but I stuck with them because I had read about AKers finding the Russian 6P14P-EV's sounding not so great at first. The graininess has gone away in my 6v6's. They're sounding pretty good at this point.
 
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I've got a quad of Soviet-era 6v6 clones (6P6S) I stuck in my amp. They were quite harsh and dead for the first few hundred hours.

Give the tubes time. Most "new" tubes I've dealt with sounded better after getting worn-in. I used to think it was just the brain getting used; but when you can compare old tube to new tube...it's been obvious that's not the case. I did have some Sylvania NOS JAN-5963's sound stellar from day 1 and only get better.

YMMV. But I wouldn't try to form a real opinion on a tube in it's first 50 hours of use. My 6P6S power tubes have REALLY opened up and they're more musical than the JJ 6V6S tubes I was running it in.
 
Run them a while. They're one of the few places I've very definitely heard break-in. I got it from my 6P14P-EV's and from the EH7868 tubes that were made in the same factory.
 
Thanks all. Honestly, once the 5670s were out of the equation, I couldn't tell the difference between the Chinese and Russian power tubes.

I did buy the RCA Command 5670s. They seem to be universally lauded on the Interweb. Not the 5670 per say, but the RCA Command in general.
 
Wrong tubes?

Wait, you said you purchased 6P1P-Ev. If so that is the problem. Completely different tube. You need 6P14P-EV. The 6P1P-EV is electrical equivalent to the 6AQ5 or EL90. Though the 6AQ5 & EL90 are 7 pin tubes the 6P1P-EV is a nine pin. The 6P14P-EV is a direct replacement for EL84, 6BQ5, 7189 tubes. Verify which tubes you have purchased.
 
electricroo said:
Wait, you said you purchased 6P1P-Ev. If so that is the problem. Completely different tube. You need 6P14P-EV. The 6P1P-EV is electrical equivalent to the 6AQ5 or EL90. Though the 6AQ5 & EL90 are 7 pin tubes the 6P1P-EV is a nine pin. The 6P14P-EV is a direct replacement for EL84, 6BQ5, 7189 tubes. Verify which tubes you have purchased.
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You are correct sir. So many numbers, so few brain cells. I quoted the wrong equivalency. This is in fact a 61PT amp (6AQ5 functional equivalent), and the 6P1P-EV is the only rolling option for power tubes. If I wanted to, I could get 9pin to 7 pin socket adapters and plug 6AQ5 tubes directly. However, the Russian military tubes have gold plated pins, are robust, abundant, and cheap!
 
thats a new one on me. I didn't catch the numbering either, but I also had no idea this tube existed. 9 pin version of a 6AQ5 on the cheap, eh? I wonder if socket adapters to octal bases could be made for a 6V6 sub. Probably not worth it, as cheap and available as a 6V6 is. Might be a nice tube to build an amp around if you're not upset about limited rolling options.
 
Have you checked to see if the Russian tubes are biased correctly (pulling the appropriate amount of plate current at idle)? If they're biased low (too little plate current), things can definitely take a ragged turn (crossover/notch distortion).

Even on cathode-biased amps, it can take a change in the cathode resistor to get it dialed in... that might be what needs to be done.

Regards,
Gordon.
 
gadget73 said:
Might be a nice tube to build an amp around if you're not upset about limited rolling options.
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At $20.00 per matched NOS quad from Mother Russia, and dirt cheap shipping, it's really a no brainer. And there must thousands upon thousands available.

electicroo said:
AH, I see. Would that happen to be a Sophia Electric Music Baby? If so it will be harsh until break in. Sophia recommends a 50 to 100 hour break in on that one.
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Now that you mention it, I had read that previously and forgot all about it. Nice detective work.

GordonW said:
Have you checked to see if the Russian tubes are biased correctly (pulling the appropriate amount of plate current at idle)? If they're biased low (too little plate current), things can definitely take a ragged turn (crossover/notch distortion).
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Hi Gordon. The amp is supposed to be auto-biasing. However, users have noted that there are a pair of pots underneath the chassis. And Sophia warns about buying aftermarket tubes. In fact, the amp came with tubes in boxes indicating which position they ought to be put in. I suppose when you buy tubes from Sophia Electric, they choose tubes that measure exactly as they did fresh from the factory. No one seems to know what the bias procedure is.
 
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Doesn't the little Sophia strongly resemble a similar e-place amp?

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Pio1980 said:
Doesn't the little Sophia strongly resemble a similar e-place amp?

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Indeed it does. Supposedly, this one has better quality control and was "voiced" by Sophia Electric. Those e-place amps sell for a third of the price of the Sophia. I didn't pay full price for it though - I traded. The advantage is that Sophia is located somewhere stateside, and service and support should be readily available. But is it a tarted-up cheap Chinese amp with a few select caps and components? Yep. It's a good sounding amp though. I bought an SMSL 36 Pro with the TPA3118 chip. Nice amp, but I keep swapping the Baby back in.

I have my sights set on an Audioromy FU-29 amp now...30 wpc of class A push-pull from a single output tube (2-in-1 tube) per channel.
 
Wonder how it compares to a tarted up console amp like my Silvertone.

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