Here is a 35W audio amplifier circuit built based on single Amplifier chip STK082. This is a very simple amplifier, very easy to build and produce sound output with a fairly large power of 35 watts into 8 Ohm loads.
Skema rangkaian STK082 - 35W audio Amplifier
This amplifier circuit is suitable for home power audio devices. The STK082 amplifier specifications might lead you to believe that it can use supply voltages of up to ±43V. but I don't recommend anything greater than ±25V if 8 ohm loads are expected, although ±30V will be fine if you can provide good heatsinking.