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diy otl

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Posted on October 18, 2004 at 01:03:42
Paul Barker
Audiophile

Posts: 908
Location: North Yorkshire
Joined: November 17, 2002
 Will anyone here have knowledge of diy issues?

I once breadborded the first Rosenblit from Glass Audio/ Tube Audio Design, which I very much liked, but was side tracked into bigger and "better?" se with the 212. Probably would have been cheaper and just as good or better to continue with otl.

Anyhow someone has recently put up another design in Audio Express. Anyone read the article? Any comments?

 

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Re: Well, Transcendent Sound Is DIY..., posted on October 18, 2004 at 07:59:29
M. Vidal
Audiophile

Posts: 235
Joined: September 13, 2000
 They are offering three OTL amplifier kit models. Stereo 16w/c, mono 40 w and a SE OTL, also in kit form that produces 1.5 w/c and 4 w in mono. I have had their T8 stereo OTL for 4 years now and it's still producing beautiful music without any maintennance hassles.

 

Re: diy otl, posted on October 23, 2004 at 01:44:10
Tom Dawson
Audiophile

Posts: 1882
Joined: May 14, 2000
 I did 3 of my own design (unfortunately, 2 of them developed power supply problems perhaps because I wound my own 1400VA toroids & I suspect one may have developed an interwinding short (not a good thing in a transformer that size) & the other may have had its 'cool' turn on circuit crap out - haven't found time to fix those two yet but still running my original prototype for 16 years now - showing the amp topology itself is sound. My design is fully balanced & dc coupled (by this I mean you put dc at the input, you'll get a steady dc at the speaker terminals relative to the ground return). No servos, output stabilized by feedback, only solid state devices are in the power supplies (rectifiers & turn on circuit).

 

Re: diy otl, posted on October 24, 2004 at 09:48:48
Hans


 
what tubes are u using and how often do u R&R them?

 

Re: diy otl, posted on October 24, 2004 at 23:09:43
Tom Dawson
Audiophile

Posts: 1882
Joined: May 14, 2000
 6bk7b's at the input, 6au6's & 6bl7's in driver circuit & 6as7g's at output. Many of the tubes are original from 1988, including perhaps half the outputs. Now's probably a good time to at least replace the remaining original output tubes. I'm going to rebuild the bias and offset adjustment circuits for easier accessibility, IAC, since the original potentiometers were sort of slapped in there and require disassembly to adjust (this amp was originally going to be just a prototype for a much higher powered pair of OTL monoblocks using 6lf6's, but I liked the prototype enough to stay with it, instead and eventually sold the sweep tubes to Richardson).

 

Re: diy otl, posted on October 25, 2004 at 08:44:28
Hans


 
Is your circuit available for us to see? It sounds like a good design.

 

Re: diy otl, posted on October 25, 2004 at 10:24:15
Tom Dawson
Audiophile

Posts: 1882
Joined: May 14, 2000
 No, it's not posted anywhere, and I'm a little reluctant to do so without some sort of intellectual property protection (which I've never got around to getting) because the overall circuit topology is really substantially 'different' from anything else I've seen:)

 

Re: diy otl, posted on October 25, 2004 at 11:11:45
Hans


 
I understand, I have the same feeling regarding my OTL amp:)

 

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