The circuit was designed as Class A amplifier that would provide 24 Watts of power.The circuit operates over the whole of the input cycle such that the output signal is an exact replica of the input with no clipping.
The supply voltage can be between 34V and 46V and the quiescent current should be set to 1.7A measured through R25 (a voltage of 0.75V must be measured over R25 for a quiescent current of just under 1.7A). R23 is a trimmer and must be set to maximum resistance (10kOhm) when powering up. Then the resistance of R23 must be decreased until the the quiescent current is achieved
Here are the specifications:
24W Class A into 8 Ohm:
100mHz – 100kHz flat:
305mV input for 24W into 8 Ohm (33dB gain):
THD is very low, although I have not been able to measure it properly:
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