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Tarzan 19th May 2009 07:25 AM

Transformerless Tube Amp
I recently stumbled accross some old magazines from the early sixties.
They had a small article on transformerless power amps.
I did a quick search on the net and found the following pattent extract:
E.H. Krohn Power amplifier US Pattent 3.092.783

Here I read that the load is 600 Ohms; a bit unpractical nowadays.
Outout Power is more then adequate.

I keep on searching further and like to know if any one had or has experiance with this kind of amplifiers.

The field of usage is mainly Musical Instrument amplification. No HiFi.
How will this amp behave under the harsh road and stage conditions?


woody 19th May 2009 07:45 AM

These transformerless amps are usualy refered to as OTL amplifiers. There are several discused in this tube forum that
can drive an 8 ohm load just fine. Just do a search for OTL and read to your heart's content.

Tarzan 19th May 2009 07:55 AM

Yes, OTL, I forgot the abbreviation...
I'll do a search.
Thanks for the so obvious tip.

merlin2069er 17th June 2009 08:33 PM

Check out Bruce's amp over at Transcendent.

I picked up his audio book from the library Audio Reality - it's a good read, with plenty of his projects in it.

Steerpike 17th June 2009 11:47 PM

Philips (Holland) has a line of very good OTL amps (AG9014, AG9015, AG9018) and matching 800 Ohm hi-fi speakers (AG5005, AG5040)

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