RE: the controversial 12au7

Posted by Tre' (P) on March 15, 2023 at 10:27:08

In Reply to: the controversial 12au7 posted by Story on March 15, 2023 at 08:50:02:

"the waveform produced can run 'distorted' if implemented with the non-linear portions of the curve."

I have looked at the plate curves for the 12au7 and I can not find a linear portion. [that is not true, there is a limited area where the tube could be used and give reasonably linear results as long as you have a horizontal (high impedance) load line] The grid line spacing it wide to the left and narrow to the right for the entire width and that will lead to high harmonic distortion.

The 12au7 works great when there is a lot of feedback applied, like in a cathode follower circuit.

As a gain stage, when there won't be much feedback applied, they should be avoided.

For comparison take a look at the 6sn7 (or 6cg7) plate curves. Do you see how the grid line spacing is so much more even and how they don't scrunch together as you move to the right and down? With this tube you can run at many different operating points and get a linear (low harmonic distortion) result. You don't even need a horizontal load line to get good results, although a horizontal load is always better.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

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Follow Ups Full Thread

Topic - Pinging airtime and others regarding the 12au7 and its favored/disfavored applications - JoshT 08:15:58 03/15/23 (23)

Why not just use a 6SN7? - andy evans 04:50:24 03/16/23 (1)

I'm going to . . . - JoshT 07:25:27 03/16/23 (0)

I have used the 12AU7 with Good results. - Cougar 09:26:45 03/15/23 (14)

Oh wow! So I could do that too with my ST-70? - JoshT 09:39:37 03/15/23 (13)

RE: Oh wow! So I could do that too with my ST-70? - Cougar 12:40:22 03/15/23 (12)

Thanks! nt - JoshT 15:43:39 03/15/23 (3)

Update: I ordered a VTA Octal pcb. - Cougar 07:39:27 03/16/23 (2)

I'm looking forward to reading about your results - 1973shovel 08:33:23 03/16/23 (0)

Excellent - JoshT 08:04:50 03/16/23 (0)

RE: Oh wow! So I could do that too with my ST-70? - Mick Wolfe 15:33:28 03/15/23 (7)

RE: " he says the 6SN7 board have been a noticeable improvement" - 1973shovel 16:08:39 03/15/23 (6)

Thanks, and one clarification question - JoshT 07:29:25 03/16/23 (5)

I continue to use the adapter - 1973shovel 08:21:37 03/16/23 (4)

I ordered an adapter - JoshT 06:48:56 03/17/23 (3)

RE: I ordered an adapter - 1973shovel 07:33:19 03/17/23 (2)

Continuity meter - 1973shovel 08:07:54 03/17/23 (1)

Thanks again! - JoshT 10:57:10 03/17/23 (0)

RE: Pinging airtime and others regarding the 12au7 and its favored/disfavored applications - Palustris 09:22:54 03/15/23 (1)

Thanks and will do. I'm still a bit green on tubes. After all, I'm only 57 LOL. nt - JoshT 09:44:38 03/15/23 (0)

the controversial 12au7 - Story 08:50:02 03/15/23 (3)

RE: the controversial 12au7 - Tre' 10:27:08 03/15/23 (1)

know all about it as discussed before - Story 10:33:53 03/15/23 (0)

Interesting. Thanks! nt - JoshT 09:45:46 03/15/23 (0)

Follow Ups

RE: the controversial 12au7 - Tre' 10:27:08 03/15/23 (1)

know all about it as discussed before - Story 10:33:53 03/15/23 (0)

RE: the controversial 12au7

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