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