U can also use this circuit, no need for cut-out circuit on PSU pcb.
Regards
Attachments
By the way, this might be a silly question:
You have designated some resistors as "FP" (example gate resistors) in your all drawings. Does it means something special?
If U use circuit in post #161 one BC546 for bias must be on heatsink with outputs fets. Sakis already answer about FP.
Regards
In post #1 U can find picture of this amplifier with 5 pairs mosfet which worked on +/-90V, but not for PA.
Regards
With new bias circuit on HV350, bias current can be setup at higer value than HV23. Also with new VI limiter there is no need for cut-out protect on PSU and protect PCB.
Clip indicator
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. Sorry for my English.
Regards Mile
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. Sorry for my English.
Regards Mile
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I prefer stability in amplifier, who prefer value with 10pF instead 100pF amplifier have perfect square at 20kHz, but I do not recomended.