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    Building, troubleshooting and testing of these amplifiers should only be
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12AX7, 12AU7 Substitution

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Joined 2003
You can't. They are entirely different valves. Don't fret about not having any ECC82, it's not a very good valve. The most expensive substitute for an ECC82 is the 6SN7, but an even better (and usually one quarter of the price) substitute is 14N7. Obviously, neither of these are plug-in substitutes but if you're at the design stage, going for 12V heaters and bigger valves is no problem at all.
Joined 2004
Paid Member
Hi Sy,
That design came out of Rainer Zur Linde's "Build Your Own Audio Valve Amplifier" book.. There are some quite interesting global feedback pre-amp circuits in that book with tone, balance, and volume controls inside the feedback loop.. I have the book, I guess originally translated from German. I bought the book at a time when I was curious about what other people were doing, and had no intention of building the designs presented. Indeed I never do, have to reinvent the wheel as you already know, that's at least half the fun of this hobby..

To Valvomaniac,
I'm with Salas on this one, sell about 2/3 of them on eBay.. Depending on what they are they may be quite popular with guitarists or owners of vintage hifi..

Instead I would purchase some 12BH7A, 6FQ7, D3A, 5842, 6SN7 - all are far better sounding than the typical 12AU7A.. There are a few good 12AU7A made by the likes of Amperex Holland or Germany, Philips Miniwatt E82CC, Mullard, Valvo, and Mazda. All of these are quite a bit better than the garden variety GE, Sylvania or RCA 12AU7A. I like the Amperex a lot and the Mazda are particularly nice sounding and are surprisingly linear too. (I used them in an srpp line stage which had <0.05% thd at 5Vrms out on a 280V supply, not bad at all..) All of these are likely to be expensive, but perhaps if you hunt around Cairo you might find some..
Eurica :idea: !!!

I'll use them to build a Dynaco stereo preamp. & a Leak stereo 20 &, &, & ! (Thanx d2134)

I've found a couple each of Amperex & Telefunken 12Au7's/ECC82's :wiz: so these will do the job, at least for now.

Salas, Kevinkr,
I never sell tubes, I hoard them! You should see the mint 100 tube carton of ECC83's, I'll keep it as a work of art! :D

Thanx guys, you've been very helpful. :wave2:
Joined 2001
Paid Member
I believe it is possible to use many of the !2AX7s are ouput tubes in a power amplifier -- IIRC there is an EAR amp using this configuration... a lot of work wiring that many tubes....

You would be better off -- as mentioned previously -- to sell the notable ones on ebay, You could be very surprised at the return -- especially if you have any Telefunken or Philips (Valvo/Mullard/Amperex/Mazda) in your stash (for the latter you need to be looking at the little codes and not the brand name)

Here is a good example (excuse the errors in my listing -- leftovers from a set of 3 Eico/Mullards) with a link to the web page that lets you understand the little codes.With the Philips family also keep an eye out for the long plate variety (17mm long grey plate, a D-getter & copper "grids"). With TFKs smooth plate seems to be worth more money than ribbed plates (a TFK will have a diamond embossed on the bottom of the tube)


This link is also useful to help identify American tubes.


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