Current in production 6072/ 12AY7 tubes

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rock soderstrom

Tour de France
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Oct 14, 2009
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Hi, current in production 6072/ 12AY7 tubes. Which is the best* and how do these compare to old NOS tubes from american manufacturers? Of particular interest is the application as a tube in microphones or as V1 tube in microphone preamps.
AFAIK, current producers/ labels are: EHX, TAD and JJ.

What are your experiences and opinions?


* best in microphonics, noise and sound
 
TAD don't make tubes, they just rebrand and test, right?  Probably not for noise either. 

I've used the EH, bought 30 of them to retube 3 RCA consoles (24 tubes), like any they require burn in and noise selection.  I was able to retube the consoles successfully with noise beating the spec in the manual, only a few rejects.  NOS?  Unaffordable in that case, and likely more noise duds to be found in such a large sample.  No obvious complaints with sound in this application. 
 
EmRR said:
TAD don't make tubes, they just rebrand and test, right?  Probably not for noise either.

Yes. Also they don't have the best prices and service...

Dirk also tests for noise and microphonics: https://www.tube-town.net/ttstore/Roehren/JJ-Electronic/JJ-12AY7-6072-V1::8022.html
Since the shop is mostly built around guitar amps, the selected tubes are labelled V1. What the criteria for selection are I don't know.
 
I don't use 12AY7 tubes but I have bought  lot of current production and NOS tubes whilst developing and building tube mixers.  I use mainly 6922/E88CC and 12AX7WA. Many so called NOS tubes perform very poorly where noise is concerned and they are often overly expensive. Of the current production makes, EH make the most reliable 6922 by far. JJ types can have better performance but they are vaery variable and the failure rate is higher. The only 12AX7WA I use is made by Sovtek which I have found to be consistent low noise and very reliable.

Cheers

Ian
 
EmRR said:
TAD don't make tubes, they just rebrand and test, right?  Probably not for noise either. 

I've used the EH, bought 30 of them to retube 3 RCA consoles (24 tubes), like any they require burn in and noise selection.  I was able to retube the consoles successfully with noise beating the spec in the manual, only a few rejects.  NOS?  Unaffordable in that case, and likely more noise duds to be found in such a large sample.  No obvious complaints with sound in this application.

Thanks a lot for your response. TAD only seems to rebrand tubes from China or Russia but they claim that they perform very strict quality controls:

- Low Noise Test
- Microphonic Test
- Gain Test
- Sonic Tests
- Shock Tests
- Listening Tests
- Balanced Output Test


http://www.tubeampdoctor.com/en/shop_TAD_Premium_Tubes_TAD_Pre_Amp_Tubes_SELECTED/12AY7_6072A_HIGHGRADE_TAD_Premium_Selected_4676

I find it hard to believe that, especially the "Listening Tests" ;) Maybe this is more marketing than reality...

@Ian:

Thanks for your experiences. I own a lot of old European tubes, most of them perform really good, but some of them became microphonic over the years. I have also had very good experiences with JJ tubes, mostly E88CC. The only broken new (out of the box) tube I've ever had was an EH 12AX7, she had lost her vacuum and turned white!  :p This is certainly no scientifically based statement due to the small number of test objects, it only shows how different experiences can be.
 
I've used about 8 or so eh 12ay7  ... they measured very well ...  around 6 of 8 were very usable in first-stage gain applications. The other two were somewhat lower emmission.

Matching across stages seemed to be reasonably consistent, but selecting for this would also eliminate prolly 2 in 8 again.

Signal-hum margin (in a high-gain application)  was very good, about the same as the eh6922 (different type pinout, lower mu and rp) and just a little less than the jj5751 (same pinout, higher mu and rp).

Harmonic distortion spectrum was nearly all h2, with low and sparse h3+  and very similar to the eh6922 and jj5751.  Most of my 12AX7, in contrast, have much 'busier' harmonics h3,  and greater.

....

So, in my experience, eh12ay7  is a very good performer .. I use it alot in place of the ax7, where it can tame some of the 'over the top' gain and attendant increased thd, particularly in the higher registers.

IF I need that extra bit of gain, I use a jj5751 - it retains that nice, sparse higher harmonic distortion distribution but with a dB or two extra level.

...

I have a few ge 6072 nos tubes, which were reasonable pricey ...

They did perform very well too, but surely didn't 'eclipse' the modern eh version .... possible one could convince onself ( as I have!) that it sounds a bit more 'refined' despite no real advantage in the basic measures  ;D

So, for some 'signature pieces' there can be a good case for fine nos, priced accordingly, but for most everything else, well selected current production  can measure a decent bit better! 

So, big fan of current production  eh 12ay7 and jj 5751 in a high gain app.
 
ruffrecords said:
The only 12AX7WA I use is made by Sovtek which I have found to be consistent low noise and very reliable.

Cheers

Ian

Have you stopped using 12AX7WC that you mentioned some time ago? If so, is there any particular reason?
Years ago somebody tested same type of tubes and found out anode hight influences harmonic spread, unfortunately at least 9 pin tubes with big anodes can become microphonic quite soon.
 
Thanks alexc for your input!


alexc said:
I've used about 8 or so eh 12ay7  ... they measured very well ...  around 6 of 8 were very usable in first-stage gain applications. The other two were somewhat lower emmission.

Matching across stages seemed to be reasonably consistent, but selecting for this would also eliminate prolly 2 in 8 again.

Signal-hum margin (in a high-gain application)  was very good, about the same as the eh6922 (different type pinout, lower mu and rp) and just a little less than the jj5751 (same pinout, higher mu and rp).

Harmonic distortion spectrum was nearly all h2, with low and sparse h3+  and very similar to the eh6922 and jj5751.  Most of my 12AX7, in contrast, have much 'busier' harmonics h3,  and greater.

....

So, in my experience, eh12ay7  is a very good performer .. I use it alot in place of the ax7, where it can tame some of the 'over the top' gain and attendant increased thd, particularly in the higher registers.

IF I need that extra bit of gain, I use a jj5751 - it retains that nice, sparse higher harmonic distortion distribution but with a dB or two extra level.

...

I have a few ge 6072 nos tubes, which were reasonable pricey ...

They did perform very well too, but surely didn't 'eclipse' the modern eh version .... possible one could convince onself ( as I have!) that it sounds a bit more 'refined' despite no real advantage in the basic measures  ;D

So, for some 'signature pieces' there can be a good case for fine nos, priced accordingly, but for most everything else, well selected current production  can measure a decent bit better! 

So, big fan of current production  eh 12ay7 and jj 5751 in a high gain app.
 
rock soderstrom said:
TAD only seems to rebrand tubes from China or Russia but they claim that they perform very strict quality controls:

- Low Noise Test
- Microphonic Test
- Gain Test
- Sonic Tests
- Shock Tests
- Listening Tests
- Balanced Output Test


http://www.tubeampdoctor.com/en/shop_TAD_Premium_Tubes_TAD_Pre_Amp_Tubes_SELECTED/12AY7_6072A_HIGHGRADE_TAD_Premium_Selected_4676

I find it hard to believe that, especially the "Listening Tests" ;) Maybe this is more marketing than reality...

A friend bought TAD's preamp and two 6L6 tubes for Fender Pro Reverb. All tested as written by you and 1 China 6L6  became microphonic after a few hours, JJ ECC803S from reverb output lost so much plate dissipation it had to be replaced after ~ 1 year. They replaced 6L6, reverb tube should live longer imo.

I searched for reliably tested EH (and Sovtek if available) pream tubes on eBay, TAD, Tube Town and a few other known shops with no luck. Banzai only matches them, no one tests EH for noise. I think it makes more sense buying a few more from reputable seller who sells a lot, test in the circuit. EF86 type has higher failure rate, although we don't use them often and not all are at V1position (V72, V76).
Btw, can't understand why no one tests them for real. They might earn more by selecting other or nos, EH is rarely problematic for inputs. So people knowing this probably wouldn't spend extra money for "some" testing. Guess it is more about marketing than real testing.
 
My3gger said:
I searched for reliably tested EH (and Sovtek if available) pream tubes on eBay, TAD, Tube Town and a few other known shops with no luck. Banzai only matches them, no one tests EH for noise. I think it makes more sense buying a few more from reputable seller who sells a lot, test in the circuit. EF86 type has higher failure rate, although we don't use them often and not all are at V1position (V72, V76).
Btw, can't understand why no one tests them for real. They might earn more by selecting other or nos, EH is rarely problematic for inputs. So people knowing this probably wouldn't spend extra money for "some" testing. Guess it is more about marketing than real testing.

I hear you, I will test them in circuit. I have just bought a GE6072 5 star and EH 12AY7, now I need a JJ and a TAD for a shootout. I am curious about the results.
 
In those 30 EH's, the difference in noise was a 16dB spread for one burn-in condition.  Higher current burn-in seemed to make a permanently noisy tube, and a lower current burn-in stuck in the higher current slot retained it's lower noise floor.  I considered the higher current burns to be ruined by the process.  They were  all 3-6dB noisier than the absolute worst of the others. 
 
EmRR said:
In those 30 EH's, the difference in noise was a 16dB spread for one burn-in condition.  Higher current burn-in seemed to make a permanently noisy tube, and a lower current burn-in stuck in the higher current slot retained it's lower noise floor.  I considered the higher current burns to be ruined by the process.  They were  all 3-6dB noisier than the absolute worst of the others.

Low and high current for burning is and its consequences is interesting. Not something I have come across. . Can you remember the actual current values used?

Cheers

Ian
 
BC-2B PRE versus PGM or MON.    I haven't done the current calculations.  I'm clearly making an assumption its current related, may be a different mechanism. 

PRE 220K P 166V / 8K2 K 3V8
PGM 56K P 153V / 1K2 K 2V1
MON 39K P 188V / 1K2 K 2V4
 
EmRR said:
BC-2B PRE versus PGM or MON.    I haven't done the current calculations.  I'm clearly making an assumption its current related, may be a different mechanism. 

PRE 220K P 166V / 8K2 K 3V8  = 0.45mA
PGM 56K P 153V / 1K2 K 2V1  = 1.75mA
MON 39K P 188V / 1K2 K 2V4 = 2.0mA

Assuming the last two figures are cathode resistance and cathode voltage then currents are as appended above. Pre is significantly lower than Mon or Pgm.

Cheers

Ian
 
Good local EH seller told me to burn in E88CC (18mA in parallel), then apply low signal input for 30 minutes and go high as much as needed after that. I didn't ask why but i will, he just told many EHs retain low noise after such procedure. He doesn't have enough experiences with EF86 and similar, so i do it in similar way with typical ~1mA as used for input stages. Triode wired with 3-4mA in BA-2 output didn't make it any noisier than input tube. A few tubes of course doesn't show real picture, i can only say burning in many EH EF86 my way doesn't make much difference if tubes are good from the start.
I'm avoiding nos because too many are microphonic or noisy, triodes and pentodes, seems like good stuff was sold until now or is waiting audiophiles. There are still some exceptions...
 
I did, as well as adding the ecc88 type in the comments section. It's frame grid of course, which might be more difficult/expensive due to the thinner grid wire, but we'll see :)
 
Last edited:
Apologies for the very tardy reply to this post

Have you stopped using 12AX7WC that you mentioned some time ago? If so, is there any particular reason?
Yes, I only use WA at the moment simply because they are the most consistently quiet both in self noise and microphonics
Years ago somebody tested same type of tubes and found out anode hight influences harmonic spread, unfortunately at least 9 pin tubes with big anodes can become microphonic quite soon.
I did that with a significant number of 6CG7 tubes. The long plate version had significantly lower harmonic distortion. I did not test them for microphonics.

Cheers

ian
 
Apologies for the very tardy reply to this post


Yes, I only use WA at the moment simply because they are the most consistently quiet both in self noise and microphonics

I did that with a significant number of 6CG7 tubes. The long plate version had significantly lower harmonic distortion. I did not test them for microphonics.

Cheers

ian
I first heard about long plates having lower distortion from audiophiles on DiyAudio or some other forum, your tests were of course much better. EH 6CG7 has pretty long plates compared to other LPs like RCA, will check your paper about types tested..
Do you think gain in twin line amp would change more than ~5dB if ECC83 was replaced with 12AY7?
 

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