need a power amp to run a set of infinity kappa 9s

Maybe Ralph's (Atmasphere) MA3 could do the job if you want tubes.

George, I recently sold three Acoustat TNT200 and a 120, all fully rebuilt by Roy Esposito in Florida. These amps are pure Fet, designed to drive the Acoustat line. Even in mono mode, they had no trouble driving the Kappas. The reason I sold them is because I came to my senses and realized my LSR&D 101s and 102s are superior in sq. I got them for an active JBL system. Anyway, it seems that the very nature of mosfets would make them especially suitable for low impedance loads, no?

Krell MDA-500

http://krell.hifihaven.com/model/MDA-500

http://krellonline.com/assets/support/MDA300500_MAN.pdf

Csontos
George, Anyway, it seems that the very nature of mosfets would make them especially suitable for low impedance loads, no?

Simply put NO, they will drive them but will run out of steam (current) at those loads below 2ohm, especially at the below 1ohm points discussed, BJT's (bi-polars) are for these speakers.

And I believe most Infinity's were voiced around Krells, as they were one of the only amps around at that time that could drive these sort of loads "with ease".

Cheers George

But as I said, the Acoustat TNT200 and 120 were designed to drive low impedance loads. In stereo, the 200 doesn't even break a sweat. In mono, they get a little warm. That's driving the Kappas. They have the Hitachi T03 2SK135/J50 and the 120 has the 2SK134/J49. Roy, who was a principal engineer at Acoustat and instrumental in designing these amps assured me that they can easily handle the Kappa 9s. He was correct.

My assertion regards the inherent nature of mosfets to thermally self-protect by reducing conduction as they heat up. Seems ideal in low impedance circumstances.