This is a simple 10 watt amplifier and should be easy to build. It is not what you would call
state-of-the-art but will produce a nice sound and a good project for the hobbyist. It can
be made using terminal strips and hand wired. This amplifier uses a single supply of 35VDC
and draws about 1.3 amps per channel at 10 watts. A power supply is needed to produce 35VDC
at about 3 amps for a stereo amplifier. The four power transistors, TIP31B, TIP23B,
TIP122 and TIP127 should all be mounted on a single heat sink. The heat sink can be a
WAKEFIELD 641-K heatsink or you can use a piece of 3" X 5" 1/8 inch thick aluminum. A blank
un-painted 3 1/2 inch aluminum rack panel cut into 2 - 5 inch pieces makes a good heat sink.
Use the illustration below as a guide for mounting the power transistors on the heat sink. Be
aware that the metal tab with mounting hole on the transistors is also connected to the collector
so it is very important that the metal surface of the transistor be insulated from the heat sink.
Applying a thin layer of heat sink grease to both sides of the mica insulator will allow heat to
transfer to the heat sink. You can also use a thermal insulator pad instead of the mica insulator
and not have to use the heat sink grease.
D1, D2, D3 and D4 should be mounted so they are near the heat sinks to sense heat from the output
transistors. Make sure the heat sinks are well ventilated. R1 and R2 are 5 watt resistors, all other
resistors are 1/2 watt.
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