"This is the cheapest 150 Watt amplifier circuit you can get,I think.Based on two Darlington power transistors TIP142 and TIP147 ,this circuit can deliver a blasting 150 W Rms to a 4 Ohm speaker.Enough for you to get rocked?,then try out this.
TIP147 and 142 are complementary Darlington pair transistors which can handle 5 A current and 100V ,famous for their ruggedness. Here two BC558 transistors Q5 and Q6 are wired as pre-amplifier and TIP142 ,TIP147 together with TIP41 (Q1,Q2,Q3) for driving the transistors.This circuit is designed so rugged that this can be assembled even on a common board or even by pin to pin soldering.The circuit can be powered from a +/-45V 5A dual power supply.You must try this circuit. Its working great."
Read more: http://www.circuitstoday.com/150-watt-amplifier-circuitSchematic Drawing
Some modifications are recommended to improve this amplifier's performance.
- Change R5 and R3 to 3.3k ohm to center the clipping point.
- Add C4 and C5 to reduce high frequency instability.
- Add C6 and C7 for power supply rail bypassing.
- Change R2 to 2K to reduce gain and increase stability.
Alternate Schematic Drawing (same circuit with mods[rev2])
With a +/- 30v dual power supply you get 64 watts output into a 4 ohm load. This test includes the above modifications and the test was done with the smaller (TIP142, TIP147) TO-220 80 watt power transistors. Most darlinton power transistors will work for the output. You can parallel output transistors, but it is best to add another pair of 0.33 Ohm resistors into the circuit.
Consider using the Current Limited Split Power Supply for Audio Amplifier
