Well, after studying the manuals for various THP amplifiers, I have an answer to my above question about the different number of active devices (FETs) used in the THP 1.1Kfx amp versus the KPA500 amp which offer rather similar power outputs.
THP essentially uses the same PA board for their 1.1Kfx (600w); 1.2Kfx (750w) and 1.5Kfx (1000w) amps by varying the power supplies and the FET drain voltage - Vd - to achieve different power levels. The PA is called the "PC1662" but with minor component changes to reflect the different drain voltages. So, the 4 FET compliment in the 1.1Kfx amp is "overkill" for the 600 watt output while being just right for their 1.5Kfx (1000w) amplifier. As usual, Elecraft got it right using two of these FET devices in the KPA500! 73, Jim Robbins N1JR ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
