From tremolu–(at)–ol.com Fri Dec 1 10:37:54 CST 1995
Article: 3844 of rec.audio.tubes
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From: tremolu–(at)–ol.com (Tremolux)
Newsgroups: rec.audio.tubes
Subject: Re: Are ALL Chinese tubes bad?
Date: 30 Nov 1995 23:58:52 -0500
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Re the 12AT7s, we’re coming from different worlds. You’re into hi-fi.
I’m into guitar amps. In a typical old Fender, the 12AT7s are run with
close to 400 volts on the plates. They’re used as a driver tube for the
reverb tank and for the phase inverter.

In the reverb driver, they just don’t hit the tank’s input transducer with
as hot a signal as an NOS tube, requiring that you turn-up the reverb
level significantly in order to achieve the right mix.

In the phase inverter, they do seem to work ok, since that stage has more
than enough gain and drive anyway. Yeah, they do “sound” ok.

Re being “weak”, they typically score at a significantly lower value on my
TV7 tube tester than does NOS examples. Since the thing measures
transconductance, they appear to have less than the NOS, by about 25%.

If they work well for you in your circuits, that’s great. But in guitar
amps, they fall just a bit short.

The only Chinese 12AT7s that do seem to work-out favorably are the ones
>from the boutique houses that test them and weed-out the duds.

Regards.