12AX7, 12AU7 Substitution

[Valvomaniac]

How can I use 12AX7's instead of 12AU7's?

[SY]

To do what?

[Valvomaniac]

Hi,

To use them in both input & driver stages.

You see I've got tons of ECC83's & no ECC82's

By the way do you know of any schematics which uses ECC83's in both stages?

Thanx

[EC8010]

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.

[d2134]

Hi,

You can use ECC83 to drive small tubes like EL84.

http://ecclab.com/schem/ecc06/110102/wzmra008.jpg
http://www.jerrycb.wz.cz/schemata/nfzs21.gif

[Valvomaniac]

I've got 120 ECC83's !!!. I have to do something with them so here is another question:

Can I use ECC83's Instead of ECC81's or the 12BH7's in this schematic?

http://www.bonavolta.ch/hobby/en/audio/6l6_4.htm

If yes: What changes do I have to make to resistor values etc.?

Please HELP me
Thanx

[SY]

No, that position is not suitable for ECC83. The ECC83 is a low current, high mu tube. The 12BH7 is a high current, low mu tube.

Is that schematic really a published design? My goodness.

[Valvomaniac]

Ok,

Any body knows of a schematic that uses ECC83's with 6L6's??

Please!

[Salas]

Originally posted by Valvomaniac
I've got 120 ECC83's !!!. I have to do something with them

Sell them on eBay, if they are wanted NOS maybe you can get $$$. Are they JAN, mixed, or single branded? European probably? Guitarists are pursuing good NOS ECC83/12AX7.

[kevinkr]

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..