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Siemens 6922 tubes?

maxhifi

maxhifi

Addicted Member
A while back I was asking about preamplifier designs, well I have been going through all of my reference materials and finally came upon a design I am thinking can get the green light.

In 1995, the UK magazine hi-fi world published an article about their KLPP1 preamplifier kit, which was designed by Andy Grove (later going on to audio note UK), and used four Sovtek 6922 tubes.

It uses a cascode input stage, followed by a passive RIAA filter, another gain stage, the volume control, and finally a single triode anode follower line stage, which has enough negative feedback to reduce gain to about x3. It also has a built in warp filter, sharply cutting off subsonic response.

Anyhow the design is appealing on a number of levels, but I am unfamiliar with the 6922 tubes, I've never used them before. I went through my tube stash and found some 80s military stock Siemens 6922, a few JAN Philips 6922, and an RCA 6DJ8. I am wondering, would these be good enough substitutes for the Sovtek tubes Andy used in the 1990s, or should I track down some Russian tubes?

Also, why is the price so high on the Siemens tubes at tubedepot.com, etc. Rarity? Quality? Maybe I would be better off to sell them?
 
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6DZ7 said:
You might use them as Christmas tree orniments... 20 on a string.
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;) I have only 5 of the Siemens 6922's, how about a string of 0A2s? Now that would look nice!
Is this a "no" vote for using the 6922s for audio?
 
6DZ7 said:
They all use the same heater pins so you can use them all. You might even try tube rolling on the string with some 12AU, 12AT, and 12AX7's since they use those heater pins, too. Merry Christmas!
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It's silly but I think a whole Christmas tree full of filaments may be pretty festive.. and I do have dozens of alligator clip leads.. hmmm :) Reminds me I have to put up the lights, hope I don't kill myself in the process!
 
That might be a nice pre. There are many options for that tube 6DJ8, 6922, and the 7308. If you have that last tube in your stock that would be a really nice one. The problem with this series of Frame Grid Double Triode tubes is that they are notorious for being noisy or microphonic. As far as manufacturers, there are many companies that made them and all have their distinct sound. I would try the auction site for tubes if you go ahead with the build. After you get things broken in you can start tube rolling better tubes.
 
Hi-FiGuy said:
That might be a nice pre. There are many options for that tube 6DJ8, 6922, and the 7308. If you have that last tube in your stock that would be a really nice one. The problem with this series of Frame Grid Double Triode tubes is that they are notorious for being noisy or microphonic. As far as manufacturers, there are many companies that made them and all have their distinct sound. I would try the auction site for tubes if you go ahead with the build. After you get things broken in you can start tube rolling better tubes.
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Thank you! The reason I mentioned the Siemens tubes, is I have four identical ones. I MAY have some 7308, it's an odd number and I wouldn't think to look for it. I got a couple boxes of Defence surplus tubes back in the 90s, and they're loaded full of cool stuff.

I've always shied away from designs using frame grid tubes, but I like the looks of this preamp design, it appears to be able to do everything I need a preamp to do. It's also cool to see a non 12AX7 based phono stage - I already have one and the appeal of something different is undeniable.
 
If this is going to be a high quality piece used for critical listening in a top end system, then using the Seimens 6922s might make sense. They are well regarded and highly sought after.

If you are aiming at a good quality piece, then you might want to consider selling off those Seimens and buying some solid 6DJ8/6922 old stock or new tubes. The Electro Harmonix 6922 aren't bad at under $15/ea.

I don't know what you could get for your Seimens, I'm assuming they aren't NIB NOS?

The Philips JAN 6922 is a decent tube, if it isn't overly microphonic. I had 4 of them, 2 were microphonic.
 
Tom Bombadil said:
If this is going to be a high quality piece used for critical listening in a top end system, then using the Seimens 6922s might make sense. They are well regarded and highly sought after.

If you are aiming at a good quality piece, then you might want to consider selling off those Seimens and buying some solid 6DJ8/6922 old stock or new tubes. The Electro Harmonix 6922 aren't bad at under $15/ea.

I don't know what you could get for your Seimens, I'm assuming they aren't NIB NOS?

The Philips JAN 6922 is a decent tube, if it isn't overly microphonic. I had 4 of them, 2 were microphonic.
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The Siemens ARE NOS/NIB, in white military cartons. I got a whole load of NOS tubes back in the 1990s, surplus when the military was getting out of tube gear. I've slowly been using them over the years, but never had a need for frame grid tubes until now. I understand that many NOS tubes are well regarded, but 6922s are really virgin territory for me, I was wondering if the Sovtek tubes were somehow more suitable for audio than the Siemens.

If the Siemens 6822 are parallel to finding a Telefunken ECC83, then by all means I will stick them in my preamp and use forever.
 
I picked up 16 Amperex USN-CEP 6922s & 7308s from a military surplus auction about 12-15 years ago. They are excellent. Purchased them for $7/ea. Later sold off 8 of them for $65 each. I ended up with 8 great tubes and $400 profit.
 
Tom Bombadil said:
I picked up 16 Amperex USN-CEP 6922s & 7308s from a military surplus auction about 12-15 years ago. They are excellent. Purchased them for $7/ea. Later sold off 8 of them for $65 each. I ended up with 8 great tubes and $400 profit.
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Tom Bombadil said:
I would say that the Siemens would be better in an audio circuit than the Sovteks.
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Thanks Tom, I will use them. The system definitely aspires towards high quality/critical listening.
 
Max,did you do much research on this unit? I seem to recall (with nothing to back this up but my failing memory) that when it came out that there were problems and general dissatisfaction with it. Do you have a schematic we could see?
 
arts said:
Max,did you do much research on this unit? I seem to recall (with nothing to back this up but my failing memory) that when it came out that there were problems and general dissatisfaction with it. Do you have a schematic we could see?
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I have the paper magazine I bought back in the 1990s, I will photograph it and post it when I am at home. My understanding is most of the dissatisfaction was around the mosfet based regulated power supply being unreliable, which I don't really intend to use, but I may not remember that accurately too. I know that hi-fi world sometimes published errors in their schematics, so I intend to double check everything before proceeding.

I basically found the design attractive because it's something besides the old RCA tube manual 12AX7 stage with passive EQ, or the 12AX7 + 1/2 12AX7 cathode follower with feedback EQ, which appear to be the two main tube phono stages out there besides the esoteric stuff which uses lots of tubes.
 
maxhifi said:
I have the paper magazine I bought back in the 1990s, I will photograph it and post it when I am at home. My understanding is most of the dissatisfaction was around the mosfet based regulated power supply being unreliable, which I don't really intend to use, but I may not remember that accurately too. I know that hi-fi world sometimes published errors in their schematics, so I intend to double check everything before proceeding.

I basically found the design attractive because it's something besides the old RCA tube manual 12AX7 stage with passive EQ, or the 12AX7 + 1/2 12AX7 cathode follower with feedback EQ, which appear to be the two main tube phono stages out there besides the esoteric stuff which uses lots of tubes.
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Yep,I think you're right. Power supply and schematic issues.

This was always my biggest issue with magazine construction articles. Despite (alleged!) proof-reading/building,many of these projects had serious errors and omissions that prevented the device from operating properly, if at all. Good luck trouble shooting under those conditions! And while many would publish updates to address these oopsies in later editions,if you were not a subscriber or regular reader you would never know what went wrong.

One 6DJ8/6922 phono stage I've always wanted to pirate is from the Anthem Pre 1.I had one in for service,and it was one of the best I've ever heard.
 
arts said:
Yep,I think you're right. Power supply and schematic issues.

This was always my biggest issue with magazine construction articles. Despite (alleged!) proof-reading/building,many of these projects had serious errors and omissions that prevented the device from operating properly, if at all. Good luck trouble shooting under those conditions! And while many would publish updates to address these oopsies in later editions,if you were not a subscriber or regular reader you would never know what went wrong.

One 6DJ8/6922 phono stage I've always wanted to pirate is from the Anthem Pre 1.I had one in for service,and it was one of the best I've ever heard.
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Have to say that in pre-internet days, the hi-fi world DIY supplement was a great resource. I've never actually built one of their designs, but sure learned a lot from them. I used to wait excitedly for the new issue every month. Going to have to check the schematic for the Anthem, I remember Sonic Frontiers/Anthem doing some great things in the late 90s, before the company got sold off.

World Audio Design, the people responsible for that kit, have a forum - I registered for it and intend to ask on there what the errors in the schematic were, and get all that sorted out before going forward.
 
Russian tubes are garbage compared to anything Siemens. You have the best there is, settle with it. E88CC is commonly used in high quality audio circuits, especially in more recent designs. Russian tubes were only used due to availability as well as a low budget compromise, not due to their quality (of which they have none).
 
ZOOM said:
Russian tubes are garbage compared to anything Siemens. You have the best there is, settle with it. E88CC is commonly used in high quality audio circuits, especially in more recent designs. Russian tubes were only used due to availability as well as a low budget compromise, not due to their quality (of which they have none).
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I remember those flat topped Siemens EL34s from the 1980s having a bad reputation when they were on the market, but then they became expensive once they became rare. I believe they may have been of East German origin though, and the tubes I have are marked "West Germany". Also, a lot of Russian tubes aren't exact copies of western tubes, but a "close fit". I was thinking that a modern design would take advantage of the differences, perhaps rendering it incompatible with the originals. Maybe I am over-thinking it. In any case I am happy to hear the tubes I have are useful and desirable.
 
ZOOM said:
Russian tubes are garbage compared to anything Siemens. You have the best there is, settle with it. E88CC is commonly used in high quality audio circuits, especially in more recent designs. Russian tubes were only used due to availability as well as a low budget compromise, not due to their quality (of which they have none).
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You are, of course entitled to you opinion, even if it is wrong. I have ran EH 6922's in my phono stage for years and am quite happy with them.

Mike
 
I own an Audible Illusions preamp. Came with Sovtek tubes. They were nice. Got some Siemens that we're all matched and it was definitely better. If your Siemens are matched, they are real jewels IMHO.
 
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