Allan Kimmel OTL

Alastair E · 13th February 2004, 04:04 PM

Hi,
Has anyone tried the Allan Kimmel OTL?

High power and low distortion are claimed, Looks like a good design with some interesting features!

What were your findings if you did make it, Im looking at making an OTL based on this design, and any input would be appreciated!

Ive tried finding Allan's web-site, but cant, the link I have dont work!, niether does his Email address.

Thanks!

runeight · 13th February 2004, 09:40 PM

Are you talking about this one?

Sweep Tube Monoblock

If so, MHO is that it may be more complicated than necessary for a good OTL. Of course, there were some design goals that Alan describes in the article that underly this design, including being able to drive the output tubes to positive grid. I guess it depends on what you need.

Alastair E · 13th February 2004, 10:40 PM

it is a bit complicated, but the thought of high power, and low distortion are quite appealing!
The power supplies are a bit of a nightmare arnt they!!

runeight · 14th February 2004, 03:44 AM

I think it could be greatly simplified without suffering from much decrease in performance, if at all.

For example, I would lose the positive grid feature because it drives the output tubes too hard anyway.

I would eliminate the MOSFET bootstrap and run the output tubes in pentode mode. Doing this eliminates the complicated voltage doubled +340V supplies.

Then I would simplify the driver stage considerably and apply a nominal amount of NFB.

Once all of this is done, the amp would be much, much, much simpler.

With 8 real EL509s per monoblock you can get 80W without going postive grid. Power supplies would be easy.

fdegrove · 14th February 2004, 03:53 AM

Hi,

Quote:

With 8 real EL509s per monoblock you can get 80W without going postive grid. Power supplies would be easy.

Absolutely. Take for instance the Bruce Rozenblit OTL that was published in GA, build as monoblocks with twice the amount of output tubes and the driver in // and it'll be a cinch.

If you don't want to use 6AS7s than these can be subbed for EL509/519 EI.

The diagram is here:

SIGNORE BONAVOLTA

Ciao,

13th February 2004, 04:04 PM	#1
Alastair E diyAudio Member Join Date: Feb 2004 Location: South Wales	Allan Kimmel OTL Hi, Has anyone tried the Allan Kimmel OTL? High power and low distortion are claimed, Looks like a good design with some interesting features! What were your findings if you did make it, Im looking at making an OTL based on this design, and any input would be appreciated! Ive tried finding Allan's web-site, but cant, the link I have dont work!, niether does his Email address. Thanks!

13th February 2004, 10:40 PM	#3
Alastair E diyAudio Member Join Date: Feb 2004 Location: South Wales	Yep thats the one! it is a bit complicated, but the thought of high power, and low distortion are quite appealing! The power supplies are a bit of a nightmare arnt they!! __________________ Das Beste Oder Nichts

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13th February 2004, 09:40 PM	#2
runeight diyAudio Member Join Date: Sep 2003 Location: Texas	Are you talking about this one? Sweep Tube Monoblock If so, MHO is that it may be more complicated than necessary for a good OTL. Of course, there were some design goals that Alan describes in the article that underly this design, including being able to drive the output tubes to positive grid. I guess it depends on what you need.

14th February 2004, 03:44 AM	#4
runeight diyAudio Member Join Date: Sep 2003 Location: Texas	I think it could be greatly simplified without suffering from much decrease in performance, if at all. For example, I would lose the positive grid feature because it drives the output tubes too hard anyway. I would eliminate the MOSFET bootstrap and run the output tubes in pentode mode. Doing this eliminates the complicated voltage doubled +340V supplies. Then I would simplify the driver stage considerably and apply a nominal amount of NFB. Once all of this is done, the amp would be much, much, much simpler. With 8 real EL509s per monoblock you can get 80W without going postive grid. Power supplies would be easy.

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