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AUDIO FORUMS >> General Discussion and Support >> I inherited a mystery amp
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Message started by wutsatoob on 09/24/21 at 15:32:37

Title: I inherited a mystery amp
Post by wutsatoob on 09/24/21 at 15:32:37

Hey everyone,

I'm new to audiophilia. It's not a hobby that I planned to get into. However, I have inherited an amplifier that I expect great things from. The amp is a mystery to me. It is one-of-a-kind, and hand-built by an expert in A/V.

I am posting here on recommendation, as there might be someone on this forum that knows something about the specific amp design. That is, flux-nulling, Catskin, SET, with Russian pentode, TV tube output drivers. The tubes used are 6J6A for the first gain stage and 6P36C for the drivers. I think the Russian tubes are a TV sweep amplifier, or something of the sort. One of the grids is internally tied to the cathode. Another is externally connected to the anode. I've heard that this is a way of using a pentode as a simulated triode.

I've posted a "unboxing" video to youtube, but I can't post a link here until I get a couple of standard messages posted first.

What I'm looking for is information on the amp design. I understand the SET concept and that it is highly desirable among audiophiles for its lack of zero-crossing distortion, but what is the "Catskin" variant? Why the TV tube drivers? I understand what magnetic flux is, but how does it impact vacuum tube operation and how is it nulled? And there's something clever going on with the 6J6A tubes. The triodes are not paralleled, nor are they in a push-pull configuration. I'm wondering if there is some kind of sophisticated compensation going on.

I would be most grateful for any information that anyone can share on this subject. I'll post the video link when I am allowed to.

Title: Re: I inherited a mystery amp
Post by wutsatoob on 09/24/21 at 23:55:06

This is a dummy post so that I can share my video link.

Title: Re: I inherited a mystery amp
Post by wutsatoob on 09/24/21 at 23:57:30

Link to a open-case video for the SET amp in question. https://youtu.be/ikAjMVTd5b4

I forgot to get a close-up of the innards, so if it helps you to help me, I'll get more images/video.

Title: Re: I inherited a mystery amp
Post by Lin on 09/25/21 at 01:18:00

I can't post a direct link for some mysterious reason, but if you search "catskin tube amplifier" there will be results from Audio Karma with member BinaryMike explaining the design with several lengthy posts and pictures.

Title: Re: I inherited a mystery amp
Post by Donnie on 09/25/21 at 02:02:08

https://audiokarma.org/forums/index.php?threads/catskin-class-a2-set-with-secondary-flux-cancellation.780706/

Here is the link

Title: Re: I inherited a mystery amp
Post by Lin on 09/25/21 at 03:08:05

Donnie, shows error and no thread.
Same thing that happened when I tried to link.

Title: Re: I inherited a mystery amp
Post by Donnie on 09/25/21 at 03:18:02

Lin,

I got it to work by highlighting both lines and then right clicking and then picking go to https:Blah blah ....706/

I spend too much time at work on computers. The young guys make fun of me because I don't know all of these tricks that they learned in preschool.

Way back when I went to school the computers used index cards and punch tape. Calculators first showed up when I was in High School.
I'm older than dirt and dumber than a red brick.

Title: Re: I inherited a mystery amp
Post by Lin on 09/25/21 at 03:33:07

What?
I get there quicker by searching with google and clicking on the link they provide. :)

When I got my first computer I thought I was going to learn everything about them, but soon realized that if I could figure out some of the basic things I would be doing good. :(

Title: Re: I inherited a mystery amp
Post by wutsatoob on 09/25/21 at 05:53:44

Thanks. I have searched on many combinations of the terms in question and haven't come up with much. That's why I ask.

I'll try to find the site linked through Google.

Cheers!

Title: Re: I inherited a mystery amp
Post by Lin on 09/25/21 at 06:00:39

Sorry wutsatoob I edited my post above, but didn't do it soon enough.
Sometimes I type faster than I think. :-[

Title: Re: I inherited a mystery amp
Post by EdwardT on 09/25/21 at 15:37:18

Maybe use this search term: CatSkin -- Class A2 SET with Secondary Flux Cancellation. Pretty comprehensive write up there and it seems like there are some facets that require care when handling.

Title: Re: I inherited a mystery amp
Post by wutsatoob on 09/25/21 at 15:45:19

Thank you! Brilliant information! And a powerful realization...

The amp that I inherited is the amp in that discussion. My relative was the designer of the Catskin variant. Wow. Much reading to do.