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08-21-2005 Post mapped to one branch of Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,486
Joined on 05-28-2004

Post #: 1
Post ID: 1339
Reply to: 1339
Gas voltage reference 0A2 tubes.

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.

OA2.jpg

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


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
08-21-2005 Post does not mapped to Knowledge Tree
guy sergeant
United Kingdom
Posts 258
Joined on 08-03-2004

Post #: 2
Post ID: 1340
Reply to: 1339
Re: 0A2 tubes.
National is the brand name of Richardson Electronics    http://www.rell.com/

They buy and have bought tubes from factories all over the world and rebranded them 'National'

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.

Can't be any more help I'm afraid.

best rgds,

Guy
08-22-2005 Post does not mapped to Knowledge Tree
Antonio J.
Madrid, Spain
Posts 272
Joined on 08-16-2004

Post #: 3
Post ID: 1341
Reply to: 1340
Re: 0A2 tubes.

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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.
08-22-2005 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,486
Joined on 05-28-2004

Post #: 4
Post ID: 1342
Reply to: 1341
The 150V regulators.

 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


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
08-22-2005 Post does not mapped to Knowledge Tree
Antonio J.
Madrid, Spain
Posts 272
Joined on 08-16-2004

Post #: 5
Post ID: 1343
Reply to: 1342
My ignorance
Thanks for the extensive reply. I wish I knew exactly the use the preamp is doing of them and if they could be safely replaced by those alternatives you mention. I believe they're regulators within the power supply. The problem with them is not burning them, but that if they don't keep voltage without sudden swings in spite of their being quite small, then the preamp puts out some DC offset which the power amp, which is DC coupled, sends to the speakers. The problem has been finding the 0A2 that are able to cut that DC offset from the preamp by feeding the signal tubes with really steady voltage for a long time. Many of them kept DC cut for some days, but after that time, the "swing" started again. On the other hand I "feel" more than I hear that the damn thing sounds better with "bad" tubes. The ones I'm using now I think are made in France, but are "regular" 0A2.

Best regards.
09-06-2005 Post does not mapped to Knowledge Tree
Jack 14
Posts 6
Joined on 08-23-2005

Post #: 6
Post ID: 1400
Reply to: 1339
Re: Help to identify 0A2 tube.
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 ?

I happen to have a lot of them, rebranded by almost everyone around the planet, National-Richardson "Made in England" being the most common reprint: they came in a tube lot buyed from the Canadian Forces !!! Some Sylvania versions still properly shows "Made in USSR".

I also have 0C2s made the same way...

The "sharp needle" brigh nickel-plated pins indicates a Sveltana (St-Petersburg) manufacture.
The base pins look like the ones used on the Svetlana EF86 I have also.

They differ from the standard US or British by their smaller height and by using a violet-glowing (if I remember well) gas mixture. They also have a tendency of performing bad at low currents, giving a different voltage drop each time they are fired up.
09-06-2005 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,486
Joined on 05-28-2004

Post #: 7
Post ID: 1401
Reply to: 1400
Sveltana's 0A2 tube.

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


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
09-06-2005 Post does not mapped to Knowledge Tree
Jack 14
Posts 6
Joined on 08-23-2005

Post #: 8
Post ID: 1402
Reply to: 1401
Re: Sveltana's 0A2 tube.
You're welcome, Romy.

I have still not found the original Russian "number" for those ones, but if ever I will, I'll forward you the info.

For what purpose are you using them at 22mA ?
09-06-2005 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,486
Joined on 05-28-2004

Post #: 9
Post ID: 1404
Reply to: 1402
5651 vs 0C2

 Jack 14 wrote:
For what purpose are you using them at 22mA ?

Bias supplies-decouplers, screen regulators… those types of the things….  BTW, until I load the my 0C2 with over 15mA they do not sound well…

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


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
09-07-2005 Post does not mapped to Knowledge Tree
Jack 14
Posts 6
Joined on 08-23-2005

Post #: 10
Post ID: 1412
Reply to: 1404
Re: 5651 vs 0C2
Hi Romy,

Well, I do not pretend to "know" those Rare-Gas zeners very well, neither to have "listened" (so to speak) to any. They are so low-performance devices when compared to the silicon technology that it is technically a pity, but, it doesn't prevent them to have other audible advantages over the sand-based devices. A tube is a tube, after all...

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.

I never met face-to face a tube audio amp using one, despite I have seen schematics of such +B regulators or Scr Grid regulators from time to time. CJs and ARs do not use them either...

Good listening !

J14
09-08-2005 Post does not mapped to Knowledge Tree
morricab
Posts 51
Joined on 07-13-2005

Post #: 11
Post ID: 1415
Reply to: 1412
Re: 5651 vs 0C2

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.

09-08-2005 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,486
Joined on 05-28-2004

Post #: 12
Post ID: 1417
Reply to: 1415
The same Korean company?

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 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


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
09-08-2005 Post does not mapped to Knowledge Tree
deemon
Posts 23
Joined on 05-25-2004

Post #: 13
Post ID: 1419
Reply to: 1400
Re: Help to identify 0A2 tube.

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 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 ?



It's very interesting ! Are you sure that these tubes are Russian-made ? I had never seen such a tubes here in Russia , all our gas tubes looks similar to SG1P ( shown in the right side of Romy's photo ) ....

Best regards
Dima
09-08-2005 Post does not mapped to Knowledge Tree
Jack 14
Posts 6
Joined on 08-23-2005

Post #: 14
Post ID: 1420
Reply to: 1419
Re: Help to identify 0A2 tube.

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Hi Dirma,

Unless you can prove me something else: the ones I have (0C2s and 0B2s) are printed "Made in USSR" very clearly.

I doubt that Canadian General Electric, or Sylvania, put this lettering on the tubes to conceal another origin, especially in the years before the Glasnost (not speaking of the Berlin Wall fall): that was not very popular around at the time. It was in fact more easy for them to re-print these ones as "Made in England" like the ones in the Romy's photograph. On the other hand, the stem (the molded glass part that hold the pins) is clearly Svetlana-made, so why not the whole tube ?

I believe those military-grade VR tubes to have been bought from the former Soviet Union by the british firm Zaerix (like a lot of other Soviet "bottles" during the '70s) and re-sold the world over, which can also explain the false "Made in England" reprint of the Romy's ones.
All the straight-sided 6L6GCs sold by Sylvania in Canada in the '70 were of Soviet origin also, but stamped "Made in England" !! I have understand the truth only when I have seen the first Zaerix "Made in USSR"... It also explain why my Fender 100 Bass Amp blew them up so easily also, but this is another story).

About the fact that you've never see those VR tubes before, let's say that the average american tube afficionado have never (and have almost no chance to) hold a Bendix Red Bank tube in his hands, or even a Tung-Sol 6900, despite that every US ICBM used one at some time. Maybe it is similar for you in Russia: does the 6C33C-Bs been originally used in Soviet civilian equipment, for example ?

LAST UPDATE: I think I found the real Romy's tubes ID (and mine too, by the same research).

Go to http://www.russiantubes.com/tubes.php?r=2

and select SG13P.  Compare it with the specs/dimensions of the SG1P...

Can it be that ??

Regards,
09-09-2005 Post does not mapped to Knowledge Tree
deemon
Posts 23
Joined on 05-25-2004

Post #: 15
Post ID: 1422
Reply to: 1420
Re: Help to identify 0A2 tube.

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

 

09-09-2005 Post does not mapped to Knowledge Tree
morricab
Posts 51
Joined on 07-13-2005

Post #: 16
Post ID: 1423
Reply to: 1417
Re: The same Korean company?

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.

09-09-2005 Post does not mapped to Knowledge Tree
Jack 14
Posts 6
Joined on 08-23-2005

Post #: 17
Post ID: 1424
Reply to: 1422
VR tubes stability
Hi Dima,

Yep, I really think that I get this one right: I never take the time to do any research about it until your posting came. Luckily, I got the clues in less than 15 minutes. If only other things can be like that...

About VR tubes stability, now: 

I have read a long, long time ago, that if someone need a reliable (ionisation voltage stability and noise) VR tube, that this one have to be AGED few hundreds hours (e.g. operated near maximum current in a burn-in fixture). It was reported to stabilise both internal gas mixture pressure and ionisation characteristics, making the tube more "repeatable" in it's characteristics and less noisy.

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).

That 0C2 was used in the regulated tube Power Supply  I've made to "feed" my Wireless Set #19MkIII (That I operated "bootleg" with few friends having the same setup: the whole kit was sold for $50 in army surplus depots at the time) and I had to readjust the output voltage (B+1 - 275V) periodically when I used the new VR tube, but not with the old. Few months of operation later, the new tube was stable as a rock. I have also used a steel shield around that tube to cut the magnetic field's influences. 
I also have some '50 vintage RCA 0B2WAs, with the boxes stamped "AGED".  When I used one, I observed a stable ionisation path within.

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
09-09-2005 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,486
Joined on 05-28-2004

Post #: 18
Post ID: 1425
Reply to: 1424
Shielding the gas stabilizer?

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 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 ?

Interesting, Jack. I have two old-school quite experienced guys who taught me that my OA2 should be shielded. Ironically, when I looked inside of my Fluke 407D power supply (from 70s), that uses the similar gas tubes use then I’ve seen that all gas tunes were shielded. I figured… “What the hell… perhaps….” In the Milq I use VR150, and in VERY critical position so, I did try to shield them. I tried at least ten different brands and I was not able to detect any change of sound when I shield any of them. Beside, those gas tubes glow with beautiful purple light… and I feel to shield them is a barbarianism! :-) Seriously, Jack, can you give some pints about yours, and some other’s, suggestions to shield the gas stabilizer tubes.  I appreciate your help.

Rgs,
The Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
09-10-2005 Post does not mapped to Knowledge Tree
deemon
Posts 23
Joined on 05-25-2004

Post #: 19
Post ID: 1426
Reply to: 1424
Re: VR tubes stability

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Hi Jack , it's very interesting !

 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



Of course , both tubes , good and bad , were used , but I think that after it they were "unemployed" for many years . Good tube needed only 3 hours of training to stabilize its voltage , but the bad one needed 3 days ........... I think that little amount of air did penetrate inside the glass , and was absorbed during the training .

Best regards
Dima
12-07-2005 Post mapped to one branch of Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,486
Joined on 05-28-2004

Post #: 20
Post ID: 1842
Reply to: 1339
The noise-free gas regulator tubes.

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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 wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
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  »  New  A resistor between screen and grid..  How the 6E5P picks microphonics....  Melquiades Amplifier  Forum     9  64296  10-20-2005
  »  New  Headphone amplifiers. Baby Melquiades?..  The survival guide...  Melquiades Amplifier  Forum     27  196511  11-25-2005
  »  New  The Melquiades' "Remote Biasing"..  The Melquiades' "Remote Biasing"...  Melquiades Amplifier  Forum     0  13871  02-05-2008
  »  New  The Shielding Condoms on those tubes......  The Shielding Condoms on those tubes.......  Melquiades Amplifier  Forum     0  16738  09-21-2009
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