From mj–(at)–ookie.pass.wayne.edu Sat Aug 27 09:01:35 CDT 1994
Article: 26601 of rec.music.makers.guitar
Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!europa.eng.gtefsd.com!ulowell!vtc.tacom.army.mil!news1.oakland.edu!news
From: mj–(at)–ookie.pass.wayne.edu (Michael J. Edelman)
Newsgroups: rec.music.makers.guitar
Subject: Re: HELP Identifying which TUBE to use (12AX7
Date: 26 Aug 1994 14:12:51 GMT
Organization: Wayne State University
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Message-ID: <33kt93$7a--(at)--ak.oakland.edu>
References: <1994Aug26.120111.80--(at)--aramount.nikhefk.nikhef.nl>
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In article 80–(at)–aramount.nikhefk.nikhef.nl, templo–(at)–aramount.nikhefk.nikhef.nl (Jeffrey Templon) writes:
…
>Blew up a couple of tubes in my amp last weekend. First time.
>In the back, there is a diagram:
>
> 6 6 12 12 7 12 7 7
> L L A A 0 A 0 0
> 6 6 T X 2 T 2 2
> 7 7A 5 7 5 5
>
>
> ^ ^ these are the ones that don’t glow.
>
>They are both actually not 12AX7A or 7025 tubes, but ECC83. I have
>seen that ECC83 is the same as a 12AX7 and have also heard that
>an ECC83 is the same as a 7025. What I am guessing is:
>

These days 12AX7 = 7025 = ECC83 (British). There’s really little difference.
In the olden days, the 7025 was a special 12AX& for instrumentation, having
low microphonic and noise characteristics. The 12AX7A was an ‘improved’ 12AX7.
Maybe. 😉 Anyways, consider today’s versions functionally interchangeable. You’ll
find more difference between brands than between tubes from the same mfgr
labeled 12AX7, 12AX7A, 7025 and ECC83.

The 12AT7 is identical to the 12AX7 but has about 20-30% less gain.
Some people put 12AT7s in the preamp section to get a cleaner sound; some put
12AX7s in place of the 12AT7 in the phase splitter stage to get more crunch.
You can experiment with this if you like.

–mike