seek a threashold power amplifier

Threshold didn't make a 1 horsepower Class AB amplifier in the 80s. They did make one in the late 80s/early 90s. It was called the S/1600e. It used the same chassis as the top of the line Class A SA/12e but was biased to operate in AB.

From my book...
Rated output: 1 horsepower @ 8ohms @ <0.15% distortion
Bandwidth: flat @ DC to -3dB @ 100KHz
Slews rate: 100 volts/uS
Output current capability: 35 continuous/200 peak amperes
Power: Two 1.2KWatt transformers & 216,000uF capacitance
Input Impedance: 50K ohms RCA/600 ohms XLR
Output Impedance: 0.1 ohm
Gain: +32.6dB
Weight: 130 lbs each

Personally, I prefer the higher biased class A designs at lower wattages. YMMV.

You might have more luck finding a pair of SA 12e's and sending them to some one like Jon Soderberg of vintage amp repair to have them re-biased to the S 1600e's specs. The SA 12e's pop up from time to time, but the S 1600e's not so much.

Unsound - I don't know for sure about the Thresholds - but it may not be that easy as the higher wattage requires a higher rail voltage which would require a different transformer not to mention that the components (Capacitors/Transistors) in the circuit may not be rated for the higher voltage required. Just adjusting the bias current does not "make' more watts.

Its all a matter of how much heat one is willing to accept or how much heat the sinks can dissipate. Rail voltage x bias current = heat (W) so if you turn down the bias current you can "turn" up the voltage (not that easy, requires changing the transformer) and your amp would have more watts, but less of them in class A because of the reduced bias current,

I have found that most output devices have a "sweet spot" as far as voltage/bias current where they sound the best - running them at a higher voltage to my ears makes the sound "harsher"

Thanks

Peter

I've been told that the two different amps are based upon the same chasis etc.. Threshold was very conservative about their use of transistors, with only about 20% of total capability actually used. As was mentioned above, each unit had two very large trannies. Nelson Pass has written a paper which would agree with the "sweet spot" concern. Either asking Nelson Pass on his section of the DIYaudio.com site or speaking with ex Threshold tech Jon Soderberg at vintageamprepair.net would probably give the most difintive answers.

You could call Threshold Audio and see if they can help you. please see

http://www.threshold-audio.com/