It is simple to build an amplifier, using the standard and stable and reliable. The 75 W amplifier circuit presented here is capable of driving 4 ohm, but, although used in 4 ohms, this amplifier has very few errors.To be aware that there are no short-circuit output, so that when the speaker short, while the amplifier is working (with signal), there is a very real danger that may damage the transistor.
Characteristic of the 75W Transistor Audio Amplifier are as follows …
Sensitivityto 74 Watts output power – a little less than 1W (1W is 75W)
Gain– 27 dB
Frequency range(-3dB) – 10Hz to 23kHz @ 1W
THD, 1 kHz – 0.05% (typical maximum)
Open loop gain– 125dB (no load), 80dB (8 Ohm load)
Input Impedance– 22k ohms
DC-Offset– less than 100 mV (<20 mV typical **)
Noise– <2 mV at the output (-80dB unweighted ref 50W)
Source: http://www.hqew.net/circuit-diagram/75W-Transistor-Audio-Amplifier_12080.html
