From tabreau–(at)–eworleans.com Thu Mar 26 15:31:21 CST 1998
Article: 93367 of alt.guitar.amps
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From: “Ted Breaux”
Newsgroups: alt.guitar.amps
Subject: Re: 12AX7 Tube Comparisons?
Date: 25 Mar 1998 09:24:57 GMT
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> I have an Ampeg Superjet with Sovteks and would like to swap the tubes
> and see what tonal changes are affected, but I don’t want to go out and
> buy a couple of each different types?
>
> Any ideas?
>

Yes. I have done quite a bit of time consuming, tedious research with
different preamp tubes in different amps. In a nutshell, here are some
plain and simple guidelines which will get you where you want to go all for
about any amp application:

With respect to my NOS Mullards as a basis of comparison…

Chinese 12AX7A – Harsh, not very musical. Avoid.

Sovtek 12AX7WA – Brittle, thin, low gain. Avoid.

Sovtek 12AX7WB – Darker than the WA, better gain.

Sovtek 12AX7WXT – Better, quieter still, but more $$. Better suited for
audio amps.

Tesla ECC83 – Good gain, quiet, best tube for drier sounding high gain amps
(i.e. modern Marshalls). Robust internal structure, well balanced sound.

Tesla E83CC – High priced, very low noise. Save your $$, as this is only
an advantage in phono preamps!

Ei ECC83 – (Yugoslavian) – Great gain, very noticeably warmer sound, and
will warm up any amp. Best tube for Vox, Fender, vintage Marshall, and any
other vintage amp. Telefunken ‘diamond’ copy, but not as quiet. Some are a
little microphonic.

Ruby 7025STR – An upgraded, premium Chinese made tube. Anodized plates.
Reported (by “Lord Valve”) to be much better and quieter. Production
ceased.

To sum it up, I find that if you are buying Tesla and/or Ei, that you
really don’t need other brands. Preamp tube selection is very important,
and often will significantly change the sound of your amp.

Ted B.