From Dr.Distortio–(at)–bs.mhv.net Wed Jun 21 12:13:57 CDT 1995
Article: 1842 of alt.guitar.amps
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From: Dr.Distortio–(at)–bs.mhv.net (Dr Distortion)
Newsgroups: alt.guitar.amps
Subject: Re: Metal 6V6 tubes in a Vibro Champ?
Date: 21 Jun 1995 15:50:57 GMT
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Mic Kaczmarczik (mi–(at)–ts.cc.utexas.edu) wrote:
: Recently a friend of mine came across some *metal* 6V6 tubes, so I put
: one in my Vibro Champ to see what it would sound like. The tube
: worked for a few minutes but then started humming loudly and
: sputtering. Thinking the tube was bad, I tried this with the rest of
: them. All 5 of them did the same thing.
The :glass: 6V6 tubes left pin 1 unused, so Fender usually used this pin
as a “holder” for the grid stopper resistor. :Metal: 6V6s, on the other
hand, connect pin 1 to the metal envelope, presumably so that pin 1 can
be grounded and allow the envelope to act as a shield. When you put the
metal tubes in your Champ, you’re tying the metal envelope to the signal
grid and making an antenna out of the tube, thus picking up all kinds of
noise.
The metal 6V6s are not up to the punishment (spec-wise) that they’re
going to receive in a Champ, anyway, so it’s best for you to stick to the
glass 6V6GT types.
From mgarvi–(at)–anix.com Sun Jun 25 09:30:06 CDT 1995
Article: 1941 of alt.guitar.amps
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From: mgarvi–(at)–anix.com (Mark Garvin)
Newsgroups: alt.guitar.amps
Subject: Re: Metal 6V6 tubes in a Vibro Champ?
Date: 25 Jun 1995 02:53:40 -0400
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In <3s8581$sq--(at)--urly.cc.utexas.edu> mi–(at)–ts.cc.utexas.edu (Mic Kaczmarczik) writes:
>Recently a friend of mine came across some *metal* 6V6 tubes, so I put
>one in my Vibro Champ to see what it would sound like. The tube
>worked for a few minutes but then started humming loudly and
>sputtering. Thinking the tube was bad, I tried this with the rest of
>them. All 5 of them did the same thing.
Thanks for trying those out for us. Nobody else had the hair
The voltage ratings on a lot of those old tubes were dubious. So
watch it! You don’t want to smoke the transformer in your amp.
I’m surprised that all of the tubes would ‘break down’ in the
same way, but you never know.
>It is of course possible that all 5 of the tubes could just be bad.
>Is there some other factor that might make the tubes behave that way,
>though? If so, is there any way to work around the problem?
Champs in general have a couple design ‘flaws’. No limit resistor
on the screen grid, for instance. Not sure if Vibrochamps have limit
resistors or not. This can be a bad thing when marginal tubes
are plugged in. Screen dissipation problems are supposedly the
main failure mode for Champs w/o the resistor.
Some metal tubes are OK, but for the most part, stay clear. Look
around for a bit (garage sales, flea markets) and you’ll find old
American (glass) 6V6Gt’s or GTA’s. Even if they’re used, those will
probably sound the best.
Mark Garvin
