Build directions

This design is very easy to build. You can of course solder everything and then apply voltage but maybe it doesn't hurt to be a little cautious.

Start with the regulated power supply.

  • Diodes
    Polyester caps
  • Connectors
  • Then continue with the high electrolytic caps, mount all caps, also the ones located at the amp itself.
  • And final with the heatsinks with mounted regulators. The regulators don't have to be isolated towards the heatsinks. You don't need heatsinks in light duty or if you have low supply voltage.

Apply voltage, 2 x 18-33V DC or 2 x 15-24 V AC and check that you'll get plus 15 volts and minus 15 volts. Measurement points are pin 7 and 4 at IC1, N1. Disconnect the power and see to that the voltage is zero when you continue the soldering. You can have lower voltage but then you'll have to recalulate the voltage regulators.

Continue with the amplifier itself.

  • LED's
    Polyester caps
    Small signal transistors, but skip the class A circuit.
  • IC socket if you want to test different opamps but I recommend that you avoid sockets (bad contact with time). If you do want sockets, use high quality with "tulip" contacts. See the picture.
  • Then continue with the power transistors and the heatsink. Mount all three transistors first at the heatsink, then cut the legs so they become not equally long. It's much easier to fit nine pins in the holes that way.

Check the output stage

Apply voltage again and check the output stage. The LED's should be lit. Measure the voltage across R17, R18 but be careful so you don't slip. Expected voltage around 1 V. You could also apply a small signal.

Put in the operational amplifier

Now it's only one part left, the opamp. Solder it in (or put it in the socket).

The whole amp is ready.

Apply supply voltage. Measure the DC output voltage. Should be less than 5 mV.

Good luck and happy listening.