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11-25-2011, 10:09 AM
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Bass & guitar tech, FOH sound, backline rentals | | Join Date: Nov 2010 Location: Concord, NH | | | Bad Russian 12AX7 tubes on ebay?
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Purchased some 12AX7 tubes from Russia, 3 of 3 tested bad in my Dynaco Mk III amplifier with instability/oscillation causing massive shrieks and squeals. Anyone else try buying 12AX7s from Russia?
My source was: 6N2P-EV = 12AX7 = ECC83 Tubes. Lot of 8. RARE!!! | eBay
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11-25-2011, 10:14 AM
|  | Leave me alone, Mrs. Vandebilt. | | | | | I haven't bought the 6N2P's from over there, but I can at least say that the 6N6P (ECC99 equivalent) works very well.
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11-25-2011, 10:16 AM
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Endorsing: Ampeg | | Join Date: Apr 2005 Location: Apopka, FL | | A lot of 8 unlabeled Russian 12ax7's for $16 on Ebay and only 3 were bad? You did pretty good 
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11-25-2011, 10:18 AM
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Head Tinkerer, The Flufflab | | Join Date: Mar 2009 Location: California | | | Don't the 6N2P and 12AX7 have different pinouts for the heaters?
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11-25-2011, 11:01 AM
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Bass & guitar tech, FOH sound, backline rentals | | Join Date: Nov 2010 Location: Concord, NH | | | NO, NOT 3 bad out of 16. Only tested 3 so far and ALL 3 tested so far are bad. Major shrieks and squeals. Did not bother to test any more after 3 for 3 testing bad. Caveat Emptor!
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P&W #924, 70 EB-3, 79 Rick 4001, 90s Tbird, 57 P bass, AFB200, SVT-810E Classic, SVT-450H Classic, RH450, Yamaha PB-1, QSC PLX1804, JBL MP255S 2x15 sub, HX410, Presonus 24.4.2
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11-25-2011, 11:05 AM
|  | <---Shinola Shite--^ | | Join Date: Dec 2010 Location: Manitoba, Canada | | Quote: |
Originally Posted by UncleFluffy Don't the 6N2P and 12AX7 have different pinouts for the heaters? | That's what I thought. You have to mod the socket wiring.
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11-25-2011, 11:24 AM
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Endorsing: Ampeg | | Join Date: Apr 2005 Location: Apopka, FL | | Quote:
Originally Posted by gnjpowell  NO, NOT 3 bad out of 16. Only tested 3 so far and ALL 3 tested so far are bad. Major shrieks and squeals. Did not bother to test any more after 3 for 3 testing bad. Caveat Emptor! | I could have told you that without buying any! Just remember the saying my dad invented, "If it sounds too good to be true, it is."
Well, HE thinks he invented it
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11-25-2011, 11:32 AM
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Bass & guitar tech, FOH sound, backline rentals | | Join Date: Nov 2010 Location: Concord, NH | | | If you have to re-wire anything then they are not equivalent. I knew I was rolling the dice I took a chance - and I lost... Caveat Emptor!
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11-25-2011, 11:39 AM
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Head Tinkerer, The Flufflab | | Join Date: Mar 2009 Location: California | | I've had pretty good luck with the Russian tubes I've picked up on eBay so far. They're all military-grade surplus. Not a dead one to date.
But, as above, you can't just plug the 6N2P into a 12AX7 socket and expect it to work.  12AX7  6N2P
Note the difference in pin 9. If you're working with a 6.3V heater voltage, the 12AX7 needs one side connecting to pins 4+5 and the other to pin 9. The 6N2P needs one side connecting to pin 4 and the other to pin 5. Quote:
Originally Posted by gnjpowell If you have to re-wire anything then they are not equivalent. I knew I was rolling the dice I took a chance - and I lost... Caveat Emptor! | Yeah, but if they were a direct drop-in replacement there would be a little cottage industry of people relabelling them and charging ten times as much. It's not a tricky change.
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11-25-2011, 11:52 AM
| | <---Shinola Shite--^ | | Join Date: Dec 2010 Location: Manitoba, Canada | | | Cottage industry of adapter sockets would be cool, if they sound good.
Other purveyors of these valves state the need to mod the socket, this guy doesn't. Dirty trick for the unsuspecting.
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Last edited by 96tbird : 11-25-2011 at 12:00 PM.
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11-25-2011, 11:56 AM
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Head Tinkerer, The Flufflab | | Join Date: Mar 2009 Location: California | | Quote:
Originally Posted by 96tbird Cottage industry of adapter sockets would be cool, if they sound good. | You can get adapters, but they usually cost more than a cheap 12ax7 anyway 
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11-25-2011, 12:48 PM
|  | Registered User | | Join Date: Aug 2007 Location: Toronto Ontario Canada | | | The last time I bought a 12AX7 it was about $5 for a JJ. Buying from some guy on Ebay is not such a good idea IMO.
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Paul
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11-25-2011, 01:23 PM
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Bass & guitar tech, FOH sound, backline rentals | | Join Date: Nov 2010 Location: Concord, NH | | | Win some, lose some. I'll be sending 'em all back...
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11-25-2011, 01:29 PM
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Head Tinkerer, The Flufflab | | Join Date: Mar 2009 Location: California | | Quote:
Originally Posted by gnjpowell Win some, lose some. I'll be sending 'em all back... | You'll probably end up out shipping both ways. I'd be willing to take them off your hands for what you paid for them. PM me if that sounds good and we can sort out the details.
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11-25-2011, 01:47 PM
|  | Registered User | | Join Date: Jan 2010 Location: KY USA | | | Modern audio tubes/valves manufactured in Russia, Slovakia, and China typically have spotty quality control. These days, tube factories do not sort out the good from the bad. Reputable tube distributors do sort out faulty and noisy tubes. It's best to buy tubes from a good distributor who filters out the duds.
eBay is not a reliable source in many cases.
Vintage tubes command higher prices because quality control was far superior. Decades ago, tubes had to be good because hospitals and militaries used them.
As other have said, 6N2P and 12AX7 tubes are not interchangeable.
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11-25-2011, 01:58 PM
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Owner, Bill Fitzmaurice Loudspeaker Design | | Join Date: Sep 2004 Location: New Hampshire | | Quote:
Originally Posted by AwkwardLoudness
Vintage tubes command higher prices because quality control was far superior. Decades ago, tubes had to be good because hospitals and militaries used them.
| Tubes from the former Soviet bloc still tend to be quite good, because Soviet military hardware continued to use tubes long after we stopped. That's partly because tubes are not bothered by EMP, partly because the Russians lagged well behind us in SS technology. Most of that hardware is still in use, still in production in some cases, and the factories supplying mil-spec tubes for them still create a superior product. It's the Chinese tubes that are not as good now, because they now make their own military hardware and since their SS technology is equal to ours they've gone SS. They've also started to clean up their environmental act, and making tubes is literally a dirty business. |
11-25-2011, 02:41 PM
| | <---Shinola Shite--^ | | Join Date: Dec 2010 Location: Manitoba, Canada | | | I've put soviet military 6p3s-e, 6l6gc equiv, coin base servo valves, In my v4b and they are great. I just wanted to try them and roll out the original 7027's. They barely get warm and are very quiet. I swear you can bounce them off the floor, they seem so sturdy. Date to 1974. Paid 8 bucks each delivered.
So, I think nos soviet pre tubes are a good bet quality wise. Sound wise is an unknown, but if you find DIRECT replacements they usually are cheap enough to roll some in for fun!, even if you get a few duds in the mix.
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11-25-2011, 02:51 PM
| | Registered User | | Join Date: Nov 2009 Location: glasgow (on the 16 bus) | | | im no expert when dealing with tube supplyers. i usually just go by what will last longest in my bassman while still giving me a good sound however i wouldent trust ebay as far as a piglet can hop.
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11-25-2011, 02:59 PM
| | | | Buy from a store or local supplier.
Stores sell EH which are tested Eastern Bloc tubes. Try Mike Kripoctkin. Great tube sales. |
11-25-2011, 04:17 PM
| | Leave me alone, Mrs. Vandebilt. | | | | | I'm interested in those tubes as well. I could use them for an amp I'm building. (if you decide to sell them)
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