Tube Preamp with tube phono section - tube Q's

[kach22i]

own a tube preamp that I bought used in late 1990's.

Have replaced four E88cc (6922) tubes about every 8-years, never replaced the four PC900's in the med/low phono section (that I can recall).

The replacement tubes have been two in the main line section, and two in the phono hi-gain section.

I have never experienced noise/grain only excessive heat, loss of both channels or weak channels in either R&L that migrate randomly between R&L prior to replacement.

These failings happen in both CD and LP playback, not just one or the other. In other words, in the line stage.

I have always used the medium phono gain at 47k for MM cartridge. Never used a MC and do not plan to.

Question: from the diagram in lower left, the two tubes labeled "phono hi-gain", do you think these are in any way active when using a MM?

Reasoning: if these tubes have never been used then I perhaps can rotate them into the line-stage section, right?

The price of these small preamp tubes is kind of crazy, and I do not have a tube tester. Just looking to be frugal but safe.

 

[DeadWax]

You're worried about trying old, possibly non-engaged 6922 tubes as replacements? They aren't going to explode if they are bad...they will just be noisy or one may test stronger than the other you end up with a channel imbalance. I'm not sure what your price threshold is when you say "the price of these preamp tubes is kind of crazy" but they are only $29 each. Sovtek 6922

 

[kach22i]

You're worried about trying old, possibly non-engaged 6922 tubes as replacements? They aren't going to explode if they are bad...they will just be noisy or one may test stronger than the other you end up with a channel imbalance. I'm not sure what your price threshold is when you say "the price of these preamp tubes is kind of crazy" but they are only $29 each. Sovtek 6922

Where can I get Sovtek 6922's for $29? The ones in your link are NOT in stock. They want $60 as many other vendors do for Hungarian and Russian NOS. Add more money for matched pairs and quads.

The question is simple, when using MM, are the two 6922's in the "phono hi-gain area" engaged and being worked?

I was thinking (please correct me) hi-gain would be employed when using a MC cartridge via the higher gain settings available with internal switches.

If true, then these two tubes in question have zero hours on them and need not be replaced. They can in fact be used where needed, in the line stage - in theory.

Asking, not stating as fact.

 

[DeadWax]

Where can I get Sovtek 6922's for $29? The ones in your link are NOT in stock. They want $60 as many other vendors do for Hungarian and Russian NOS. Add more money for matched pairs and quads.

The question is simple, when using MM, are the two 6922's in the "phono hi-gain area" engaged and being worked?

I was thinking (please correct me) hi-gain would be employed when using a MC cartridge via the higher gain settings available with internal switches.

If true, then these two tubes in question have zero hours on them and need not be replaced. They can in fact be used where needed, in the line stage - in theory.

Asking, not stating as fact.

Let me see if I can find another source for the Sovtek 6922's.

I'm not 100% certain but the two 6922's labeled "phono high gain" are likely the for the MC gain stage only and aren't used while low or medium MM-only stage is active.

I would give the pair a try and see how they sound.

 

[kach22i]

Let me see if I can find another source for the Sovtek 6922's.

I'm not 100% certain but the two 6922's labeled "phono high gain" are likely the for the MC gain stage only and aren't used while low or medium MM-only stage is active.

I would give the pair a try and see how they sound.

Sourcing affordable 6922's is not the problem. I resolved that days ago, see link below.

https://www.vivatubes.com/search.php?search_query=6922

The problem is my limited understanding of my tube phonostage(s).

The fact that 6 out of 8 tubes are related to phono signal amplification is actually something that never hit me before a few days ago. I always regarded the star grounded PC900's as my phono tubes.

What the heck is hi-gain phono?

The possiblity that the MC section lays dormant under my ownership and that even when I replaced and saved those tube before that they still might be good excites me - I love saving/recycling and reusing things and hate waste.

 

[kach22i]

UPDATE:

Got a reply in another forum that I am happy with.

MM and MC phono sections require use of the two 6922's in lower left hand corner of the so-called "hi-gain phono" section.

Link:
https://www.audiosciencereview.com/...preamp-with-tube-phono-section-tube-qs.14253/