Here is the 100W power audio amplifier circuit diagram build based on a pair of FET component on final amplifying process. The FET components using a pair of K134 and J49, the substitutes for these FETs are the combination of J162 and K1058. The output power will be about 100W at 8 ohms speaker. For stereo application, you should build two similar circuit.
The power supply which is used for this circuit is split / dual polarity type. This kind of circuit has three outputs that are positive, negative and ground. For stereo application, it’s better to double the power supply component (T1, C15 and C16), coz the stereo power amplifier consumes 2x energy than mono amplifier.
Then, here the PCB design for above 100W power audio amplifier circuit.
Good luck
ii have a kmd gs45b 45watt solid state bass amp, made in England in late 80’s it has fet k134 amd jk49 on the circuit board…. i read that mos/fet amps aren’t subject to thermal runaway. i know nothing about this stuff…what does that mean? the amp is a combo rated at 8ohms (with 1—8ohm speaker in the cabinet with the amp. can i add a extra 8ohm external speaker to to the amp (which will equal 4ohms) without fear of overheating the amp? does not being subject to thermal runaway have anything to do with overheating of a solidstate guitar amp? thanks for your help,,, joe