[Vintage-Audio] 12AX7 and other Tube questions

Tue Jun 11 21:34:00 2002

While 12AX7 / AT7 types often go microphonic, they rarely wear out, and are
usually NOT the source of crackles and pops. While the amp is on, and with
the volume SLIGHTLY  turned up, rock these small tubes in their sockets. If
you hear explosions etc, put a small quantity of oil ( thats right, OIL ) on
a "Q-Tip", and apply sparingly to each tube pin. Re-insert in the socket
 amp off ) and rock it around a few times. Do this until the noises stop.
With regard to 6L6 tubes-- For new, the best bet is probably the ones made
by Sovtek. As you are aware, the Chinese ones are awful.
Groove Tubes are nothing but commonly available tubes ( Mostly Sovtek /
Tesla etc )  that are "screened" / graded / and matched. For this "service"
you pay a premium price, but the convenience is often worth it.
The absolute best 6L6 types available are the 6L6-WGB / 5881 tubes made by
Tung-Sol. The average amp tech will not have these in stock, as they are no
longer being made. Antique Electronic Supply has them in stock, and the
price of these is quite reasonable. This type has higher design ratings than
commercial 6L6 types, even better than the 6L6-GC. The 5881 can be used to
sub any 6L6 type, as well as KT-66, and the hard to find 7027-A used in some
Ampeg amps.
I have been using / repairing tube amps for over 40 years, this is what I
use in my own amps.
Chuck N1LNH
-----Original Message-----
From: Philip Atchley <[email protected]>
To: [email protected] <[email protected]>
Date: Tuesday, June 11, 2002 4:02 PM
Subject: [Vintage-Audio] 12AX7 and other Tube questions


>Hello
>I'm new to the list so please forgive me if this has been covered before.
>
>I got my Peavey Triumph 60 guitar amp fixed and working.  (channel select
>relay like I suspected).  It plays and sounds quite good with just a very
>slight occasional crackle,  which I suspect is probably one of the 12AX7
>pre-amp tubes.
>
>Couple questions.
>1.  Which brands of 12AX7, 12AT7 & 6L6GC are good for use in a high
>vibration enviornment. (Like a "cranked" 60Watt 112 combo amp).  Reason I
>asked was back in the early 80's I went through about 3 changes of a couple
>of the pre-amp tubes in my Fender "twin" (blackface with 2 JBL's) before I
>got a set that didn't go microphonic right away.  When I finally got it
>right I never had another problem, but don't remember the brand.
>
>2.  Are the Sovtek tubes any good (this amp has one in the first stage that
>'seems' quiet).  I can't see paying for special "golden eared audiophile
>tubes".   Ditto for 12AT7 tubes (of which I have one NOS RCA tube)
>
>3.  All the rest of the 12AX7's are apparently original, Peavey brand "made
>in the DRG".  WHERE in the world is the DRG?  Interesting thing is both the
>Peavey and the Sovtek have the same style black printing of the
>numbers/name.
>
>4.  While on the subject of tubes for guitar amps.  Although I don't need
>them right now, what are good 6L6GC tubes for this enviornment?  Are the
>Russian brands any good?  I definitely want to stay away from any Chinese
>tubes.  And with a slim wallet premium NOS American tubes  would make said
>wallet even slimmer very quickly.  BUT, I understand that some 6L6's are
>prone to "short out" in guitar amplifiers.  I had that happen to me while
>playing on the platform at church once.   That poor little 50 Watt Combo
>sounded like a BOMB went off in it.  This Peavey is the first Tube amp I've
>had since!
>
>73 de Phil  KO6BB
>
>REAL Radio is heard on Boatanchor Receivers.
>REAL Music is played through  'Valve' Guitar amps!
>[email protected]
>Merced, Central California
>
>
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