Would anybody recognize who manufactured those 0A2 regulators?

Since I use them quite aggressively, I picked at MIT's fleamarket a few dozens of them dirt-cheap. The tube looked suspensions. Then marked as Amperex, Made in England and National Electronics, Made in England and came in original boxes. On the picture they are 3 tubes in the middle.

The suspensions  tubes have identical construction, very “third-country-like”, contemporary-looking legs and very modern printing.  Most likely someone faked them. The original Amperex has totally different construction (the tubes on the left).

Initially I thought that they might be Russian-made but the Russian’s VR150 are totally different (the tubes on the right). So, did anyone come across those tubes and have an idea where they might come from? The forged tubes do regulate perfectly fine and even sound better then few others (not the best among all though…)

Thanks you,
Romy the Cat

guy sergeant wrote:

When I worked for a UK based tube amp manufacturer some 10 years ago we had a couple of pre-amps using OA2's in shunt regulator circuits. These (physically shorter than standard) OA2's came from Richardson and did work very well being both quiet and reliable. However those we used had silver coloured pins and were 'new' production, I believe from China. The compact glass envelope and printing looks similar though.

Thanks, Guy. Most likely it’s it, since they are the smallest OA2 among all.

Antonio J. wrote:

My preamp also uses those 0A2 and I have a bunch of "made in USA" ones that look right the same than those "National", using the same orange color for the brand letters, but they're supposed to be RCA. They all failed in a quite short time in deliver de stabilized voltage they should. I guess they might be chinese. Do you know where to get reliable 0A2? They also last little here.

Hm, you keep burring the OA2? Are you sure that your preamp is designed properly and that it does not care excessive power and excessive start up voltage? A good 0A2 is very reliable: I remember that it was able to care 250mA over 2 days and was able to start up with 100uF across it – both absolutely barbaric and ridiculous modes.

Anyhow, There are plenty OA2 around and probably the best place to buy them form hum radio shops. The http://www.radiodaze.com/ has quite a large stock and there you might pay one extra buck per tube and to choose the specific manufacturer brand (do not be drooling – I have suck out from there all “kinky” brands). However, since you are far form NY then get some of your local tubes. The Europeanians produced many 150V regulators that are direct substitute of OA2: SG1P, STV150-30, 150C2, CV1832, QS1207, GD150M. If you wish to replace it with “larger” VR150 and go for the 0C2 then you might fine another half-dozen models. Anyhow, I will not comment how all-different tube and different breads sound, as I'm sure that Melquiades and your preamp use them differently. The Milq do not really use them as the regulators but as the decouplers....

Rgs,
Romy the Cat

Jack, thank you very much, it was very informative. As I understand all 150V regulators use violet-glowing gas. In my case those tubes cares 22mA and it looks like (so far) they do hold stable voltage with no noise.

Once again, thanks,
Romy the Cat

Jack 14 wrote:

For what purpose are you using them at 22mA ?

Interesting, Jack, since it looks like you know those gas tubes well.... did you ever try to "compare" Sound of 0C2 (or any other 35mA tubes) while they are drawing low current with the Sound of 3mA 5651?

The Cat

Hi,

I have a phono stage from the Korean company Silvaweld that uses the 5651 tube in the power supply as a voltage reference.  It also is using a Russian 6C19Pi tube along with EF86 pentode as the high voltage regulator.  The rectifier is a 6w4 (I think). I am not entirely sure about the actually circuitry of the phono stage  except that the front end is a cascode configuration using a 12AY7 (or 6072a if you prefer).  The sound from this stage is IMO outstanding.  My linestage, also from Silvaweld, is using a highly unusual power supply using a combination of the EF86 and a 300B as the high voltage regulator (yep, a big power triode in the power supply)!!  The tubes in the circuit consist of 1 6922 and 2 WE417a tubes per channel in a fully balanced configuration.  The sound?  IMO its at least as good as the Lamm L2.

morricab wrote:

I have a phono stage from the Korean company Silvaweld that uses the 5651 tube in the power supply as a voltage reference.  It also is using a Russian 6C19Pi tube along with EF86 pentode as the high voltage regulator.  The rectifier is a 6w4 (I think). I am not entirely sure about the actually circuitry of the phono stage  except that the front end is a cascode configuration using a 12AY7 (or 6072a if you prefer).  The sound from this stage is IMO outstanding.  My linestage, also from Silvaweld, is using a highly unusual power supply using a combination of the EF86 and a 300B as the high voltage regulator (yep, a big power triode in the power supply)!!  The tubes in the circuit consist of 1 6922 and 2 WE417a tubes per channel in a fully balanced configuration.  The sound?  IMO its at least as good as the Lamm L2.

Morricab,

I do not know this company. Are they same people who made those crazy  OTLs? I Know that there is some Korean company then make their OTLs with zillions paralleled 6C19P. I am very much no OTL-type of person but it would be interesting to hear THAT beast….

THE cAT

Jack 14 wrote:

Hi, these ones are Russian military stock: see that no mica elements have been used in their construction, like the US Bendix Red Bank tubes (used in US ICBMs of the '50's-'60's). Old Soviet ICBM spare stock ?

Hi Jack ,

Thank you for your very educational info ! It looks like you are right , and your tubes are rebranded SG13P ....  Maybe a big stock of those tubes were exported , and you know them better than we do :-)
And another question . You wrote :

"The 5651/0G3s were designed to provide a precision reference (they use a radioactive-doped gas, if I remember) for tube electronic regulators used in high-end instrumentation or communication equipment (the Collins R-390/URR use one in it's regulated PS, for example). The flip side being that they were optimized to run at low currents only."

What do you think about long-time reliability of this tube ? First of all I mean noise and fluctuations . I want to try them in a screen grid regulator for the first stage of a RIAA preamp , so the little and stable noise is important ! I have two 5651 , one tube operates very good , but another behaves a kind of strange - when I fired it up the first time it gave 100 Volts instead of 85-88 ( it's normal voltages ) and was quite noisy , but after 3 days of continious training voltage decreased to normal , and noise decreased too . I think that it can occure due to gas problems . Of course , the best idea is to replace this faulty tube ... but can I be sure that this kind of tubes will operate good later ?

Best regards
Dima

Yep the same company (they also make a VERY good sounding OTL using the 6C33C tube).  I have heard that zillion tube amp and it is also quite good (but I thought the 6C33C amps captured the "correct" tone better).  You should try to hear the SWC 1000 linestage from this company (it is what I am now using).  Something special I tell you.

Jack 14 wrote:

To sum up, it seems that if you want a stable VR tube, you should age it a few hundred hours and shield it against magnetic fields. Is it making any sense to you ?

Rgs,
The Cat

Jack 14 wrote:

When I was younger -35 years ago-, I have observed the glowing of a NEW VR tube (it was a 0C2) for few hours (ok, I had nothing more interesting to do then..) and seen that at low currents, especially, the ionisation path moves itself randomly between the tubes elements (the ionisation density is never equally distributed vs the element's surface) and that this displacement was translated as small variations of the operating voltage accross. An "old" one does not behaved like this, seeming to have a "preference path" between it's elements. But, interestingly, both were sensitive to magnetic fields (I disturbed the ionisation path at will with a small magnet, creating suddent voltage jumps across the tube). To sum up, it seems that if you want a stable VR tube, you should age it a few hundred hours and shield it against magnetic fields. Is it making any sense to you ? I do not see why the 5651 cannot behaves similarly.  Was your "bad" tube a never used one ? Have fun, but beware of the gases ! J14

If you read the post:

http://www.goodsoundclub.com/TreeItem.aspx?postID=41#41

then you know that I am happily employ an interesting 65dB-gain, 7788-7721 two stages phonocorrector designed and build with air capacitors. A few days ago when I eventually got my SPU Mono replacement I decided to finalize the design and find a correct screen supply for the input penthod.  More about it at:

http://www.goodsoundclub.com/TreeItem.aspx?postID=1818#1818

The scenario is very simple: a VR isolation tube with a driving resistor and small pre-screen stopper. However what I would like would be to get rid of a capacitor before the pre-screen resistor. There is an opinion that the nature of the gas regulators create a noise but I wonder if exist out there any ultra low noise gas 75V-105V regulators that would be able to drive the screen without any caps?

I pulled out of my storage a collection of my gas tubes and so far I use Philips 85A2. (Data is here) The noise-wise this tube it looks like is in the realm of any other VR-75, VR-105 tubes. So, are my dreams about the noise-free gas tubes an utopia?

Rgs,
The Cat

I remember when I built Melquiades I detected that quietly of wire that feeds the grid of output stage with bias, quality of soldering or any other minute detail on this  wire was very auditable. I also detected that the proximity of this wire to cassias was auditable. Understanding that anything that feeds grid is crucially important (try to play with shunt cap after the gas tube and you will kill the Milq sound) I ask myself: how about the “quality” of the gas tubes?

In Melquiades the gas tubes live after 9000uF capacitor (I do not use C12 as the PS sits very closed from output stage) and they are basically driven by DC. The gas tubes are wonderful “dumper” themselves and whatever own MF noise then generate blocked but the following stunt cap. Still, how do they “sound”, if then have any sound? The negative supply gas tube feeds the both grids and I presumed that should have some effect. The positive supply is kind of irrelevant and I did run the connected Milq without the positive supply, letting the amp to be grounded on the preamp output. I did not detect any sonic differences with or without the positive supply.

So, took some gas tubes that I had in my home now and decided to listening with all of them, trying to detect if it were any difference. As I usually do I kept a small log of my experiments and since, there WAS a sonic different in Milq with different gas tubes I decided to publish the results. A few things should be taken for consideration:

1) In Milq the gas tubes do not used like regulators but rather as “garbage absorbers” and I have no idea if in a different application the tubes might behave similarly

2)  All tubes were new and “cold”. There were identically not pre-burned and before auditioning were running for 5min in hot amplifiers (the got warmed VERY fast when you drive 25mA thought them)

3) There is an army of the 150V 7-pins gas tubes: 0A2, SG1P, STV150/30, StR150/30, 150C1, G150m 150C2, 150C4, CV10664, CV1832, CV2903, CV8161, HD51, M8223, QS1207, GD150/4K, QS1210, SR56. I did not try the larger octal 150V tubes (I very much would like to and I will)

4)  The differences that I detect were VERY minor, much less than a typical flipping of a signal tube from a “good brand” to “bad brand”.

5) Some related threads on the site:

http://www.goodsoundclub.com/TreeItem.aspx?postID=1818#1818

http://www.goodsoundclub.com/TreeItem.aspx?PostID=1339

So, I took my box of Cohiba and placed Verdi’s Rigoletto of 1956 into the game (Callas, Gobbi, Di Stefano by La Scala under Tullio Serafin. The result was following: (from left to right on the picture)

1) Holland Made Amperex with flat shield - All together correct sound, slightly more round then I would like to. The similar sound was by US’s General Electric (not on the picture). However, General Electric subjectively sounded louder but not more dynamic, juts louder.

2) German made National Servisemaster - in a way similar to above by has slightly more “yellow” tone.

3) USA’s Sylvania – very-very nice tube. Perfectly balanced and with no surprised. Dynamic vs. tone, sharpness vs. elegance… everything is perfect.

4) USA’ Tung-Sol –very interesting tube. It has some softness but some interesting attitude in it. It going down very elegantly but then suddenly jump on you but also in a very elegantly way. I do not get and I do not know if I like it but the effect is very interesting.

5) Russian SG1P – horrendous tube, absolutely the worst sound. It has tremendous slam but at the same time it completely washed out any tone. It almost sound like overly contrasty b/w picture of the a colorful landscape

6) USA’s Raytheon – a nice well balanced tube. For whatever reasons sound got “further” with this tube. Very strange affect indeed.

7) USA marked Nations – this tube is a contemporary bitch. The tube might be identified by the glossy sharp-ended pins. (on the second image 3 tubes in the middle) This is a contemporary production of Russia and the mark them as anything you can imagine (including the “original” boxes) I have seen them as Ampere, Raytheon, CVS, FEN, and God knows what. Pretty much everyone push this tube today as anything. Ironically the tube is not really bad. Sonically it is “almost” OK but it has some sharpness and aggressive that I do not like. This tube is heads and shoulders better then the Russian-made #5. Still, I feel that very-very slightly it loosing tonally to the Western tubes.

8) German made Telefunken – superbly tonally but overly soft. Also it eats some dynamic. The good parts about this tube (and completely irrelevant from my point of view) that it locks voltage closest to 150V then any other tubes – 149.98V

9) USA’s RCA – good tube but a bit too dull and not contrasty. At the same time it is not soft and has some “punch”, with a contradiction, isn’t it?

10) Another USA’s Raytheon Registered. Very similar to the #6. The effect of “further” does not manifest itself. Perhaps it is because it is a different batch?

11) Holland Made Amperex with screen shield – it is on the second image on the left – the best 0A2 that I have. Sonically it is identical to Sylvania but it has more dynamic. Tonally it is also superbly reach. A truly phenomenal performer!

The value/type of the capacitor after the gas tube hugely affects sound. I made quite a number of experiments in past with those caps and I have no idea why it is so. Well, I hardly understand (and I did not see anyone who does) why the “gassed resistor” biasing generality took the sound 6E5P way out the… So why should I understand WHY the value/type of small capacitor after the gas tube affects sound. However, it does affect it.

 If you look at the Melq’s circuit:

http://www.goodsoundclub.com/PDF/Melquiades_SET.pdf

then the cap C4 and C5 are very tricky sons of the bitches. Theoretically those caps should be irrelevant as they decupled form the tube grid by a large 390K resistor. Well, not so simple…

The circuit is very simple: a current regulating resistor, a gas tube with the following R10 and the cap across them. One of the cap’s legs sits with at the gas tube’s leg (it is critical). A gas tube creates own MF noise and the cap kills the noses. This is simple and very ordinary…

Now, I ran the amps with many different gas tube including the few versions of low current 5651 and I ran them… without C5 cap. No capacitor no problem other say – well, not so simple. Ironically when I did not use the C5 cap I did not have intolerable noise. I have some very minor MF noise that did not bother me at all. However, I did not have good sound either. The sound was vicious, erratic and reminded me a drunk driver driving. Applying, a small cap right across the tube itself (as it suggested in classic books) queried some noise but did not affect sound in necessary direction. However, placing the shunt cap after the R10 resistor did not necessary magic…

The value and type are other mysteries. 1uF, 2.2uF, 5uF did not sound properly. The 10uF for whatever reasons did. It was not that something got better or worse with raise of capacitance. The nose was killed at 2.2uF and further increase of capacitance did not affect anything… unit I reached 10uF. At 10uF is all come together making the 6E5P to sing in this application. I did true a good quality”expensive” plastic caps but it looks as “it” wants only electrolytic….

As I told before when I discovered this way to operate the 6E5P in Melquiades then was afraid to “loose sound” and did not go for anything further. Still, if a higher voltage gas regulator exists then it will be possible to use higher nominal of resistors to grid... It would always help, and particularly in the super Melq…. Sometimes in future, I plan to try two gas tubes at 300V. I do not know if pairing of the gas tubes will affects sound.  I also wonder if the increase the voltage will lead to the increase of the “best for sound” capacitor values after the gas tube…

Rgs,
Romy the Cat

Who know how they die, at least I was not able to figure it out. The literature suggest that when gas regulator at the end of their life they stop regulate or maintain regulation but increase noise. I was not able to detect it.

I have many gas regulators and measured their mutual conductance. I take the measured 100% gas tubes and the very weak tubes (the same brand) and put them in Milq – they sound identical. I went further and was trying to intentionally kill one 0A2. I drove it for 3 hours with 150mA (instead of 35MA max). The tube went hot like hell but do you think it killed it? Very much not. It still regulated 150V and it after it cooled down it sounded perfectly fine.

Since I use gas regulation in my Melquiades to damp bias and bias compensator supplies I really would like to learn how the gas tubes die and what would be a signifying fact that a gas tune at the end or it life…

Hi Romy,

Still playing with Gas zeners, isn't it ?

I once seen, tested and scrapped "dead" ones....
Clue#1: they fire and (try to) regulate at higher than nominal voltages at normal current and are erratic.
Clue#2: they have sections (at top and bottom, usually, where is the gap between the outer shell and the mica spacer) of the internal glass internally "plated" by the anode metal ions that have drifted reverse to the electron flow inside. BTW, the center rod is the Anode (positive) the external "plate" is really the cathode (negative): the reverse of a "normal" heated-cathode tube. That "ionic" plating looks like the top getter, but is more aluminum like in colour.

Such condition, I guess, cannot be acquired otherwise than by operating few THOUSANDS hours, maybe in excess of 10,000 ? I don't know... I never had enough patience to test that.

The ones I tested a long time ago (military surplus, again) that behaved like that are now lying in some burial site, I guess.

May they Rest In Pieces.....

Best regards,