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Michael Rothacher 29th May 2002 12:07 AM

Experimental Design - Comments, Flames Welcome
2 Attachment(s)
First, to the uninitiated: please don't build this circuit. It is only a conceptual schematic. I'd really like to hear the thoughts of your group and, if he would do me the honor, the "Big Guy" (NP)! Particularly, I'd like to figure out if there's a simple way to employ mosfets in the OP.



Michael Rothacher 29th May 2002 02:53 AM

MOSFET version
2 Attachment(s)
Here's the mosfet version almost ready for alligator clips and duct tape!

Nelson Pass 29th May 2002 07:22 PM

OK. but I have to think about it for a while.

Michael Rothacher 30th May 2002 04:45 PM

Excellent! Thanks Mr. Pass!

GRollins 30th May 2002 05:31 PM

I glanced at if briefly. Need to get back to painting walls, etc. My first impression is: Circlotron.
If so, bear in mind that that output stage is patented by Ralph Karsten.
I'll try to look at it in more detail later.


reinhard 31st May 2002 08:14 AM

Yes Circlotron,
I donīt kwow the content of the Ralph Karsten patent, but there are many Circlotron amplifiers out there: Einstein OTL, Audio Valve and every power amplifier from Balanced Audio Technology,
tube and transistor.

Reinhard from Germany

Michael Rothacher 31st May 2002 02:42 PM

Grey, Reinhard:

Thanks for your replies. Yes, I would say the OP qualifies as a circlotron. It does remind me of an old OTL tube schematic I saw in TAA. I had a look at the Karsten patent and I don't believe this circuit is is directly comparable. To my unqualified eye it is just a balanced bridge with batteries in two of the arms. In fact, the inspiration for the OP came from a 1960's U.S. Navy transistor book. I was originally trying to work-up something along the lines of a two stage "Son of Zen" and this where I ended up. I'm working on a currnet flow diagram to help clarify the circuit action in my mind. It is problematic at the moment, and I haven't figured out a good way to apply overall feedback. I wonder if th "X" feedback topology would work? Also I think I see an easy way to dynamically bias the OP, but it'll have to wait for the weekend. I really appreciate your comments. Please keep them coming.


Michael Rothacher 31st May 2002 03:35 PM

If I may go off topic for just a moment, I've been wanting to thank Nelson Pass for a decade or so. I built the A40 when I was in the Army, stationed in Germany, and I've been having fun with this hobby ever since, due mainly to the generous contributions of Mr. Pass. It is a terrific hobby.

Have a great vacation.


GRollins 31st May 2002 04:17 PM

I still haven't had time to go back over the circuit but, to the extent that it is (maybe) a Circlotron, yes, X will work. Keep an eye on the phase and all will be well.


djk 1st June 2002 09:19 AM
Each half of the bridge acts like a current source for the other.Only one polarity output device needed.A 50W amp could be made from one pair of IRFP22N50A ,a 277W device available from DigiKey for $2.45 .Since no devices are paralleled no matching should be needed.If you have trouble visualizing this just draw it out on a sheet of paper.Prior art shows both tube (Atamasphere) and BJT (Sumo) versions of this idea.

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