This is very simple Class-A 2SK1058 MOSFET Amplifier circuit. It is easy to build it, Must use supply volte 24V at high current. It produces the most purest sound. I have no idea of distortion levels etc. but it has a very fine grain, and delicately textured quality.
This is one package 2SK1058 N-Channel MOSFET Pin DiagramThe four resistors are 15ohm and 10W each the which I wired two in series for 30 ohms and then the two sets of 30 ohms are wired in parallel to give a total resistance of 15 ohms. These get extremely hot and burn about 30W at idle.
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