o zaštiti PSU7: Pojacalo nije samo po sebi pouzdano, posebno ne jaka pojacala gde tranzistori rade na gornjoj granici napona i struje, zato na APEX HV23 postoje VI limiteri za strujnu zastitu fetova i zener diode za prenaponsku zastitu gejtova, a na kraju i zastita od krakog spoja koja salje signal preko pina PRO na zastitu koja se nalazi na plocici ispravljaca i iskljucuje zvucnike. Na ovoj plocici je i soft-start i osigurac za trafo, napajanje za ventilator... LED za clip takodje opominje kada pojacalo radi blizu maksimalne snage. http://www.diyaudio.com/forums/solid-state/162043-mosfet-amplifier-irfp240-irfp9240-24.html o HV350: HV350 is general purpose amp, efficiency is not important, just sound, but with HV250 you have efficiency (maximum power from rail voltage for class AB amp),VAS transistors biased with 27mA, for outputs 100mA/device with proper heatsink. With high biased VAS no need to use EF with BJTs in output stage. V2: http://www.diyaudio.com/forums/solid-state/162043-mosfet-amplifier-irfp240-irfp9240-27.html If no signal on the output of amplifier voltage on point 47k,22k,10R,10uF is 25V to the negative rail, BC546 is on and short circuit led diode, current go thru GND 10k1W CE of BC546 to negative rail. When voltage on output is about -65V (-75V rail voltage), voltage on point 47k,22k,10R,10uF is 10V to the negative rail, and in the point 22k,1k5,base BC546 is 0,6V to the negative rail, BC546 off current go thru GND 10k1W led to negative rail, and LED light. 10uF give some time delay for short peaks.