200 Watts Leach-Designed Amplifier

The amplifier was designed with high fidelity that was originally built by Marshall Leach with simple construction, discrete components, enough power reserve, and good parameters.

The amplifier assembly includes a toroid transformer with 300W output and electrolytic and ceramic capacitors, carbon resistors, and zener diodes. The transistors used were made to match to avoid DC offset problems. To set diode current to 3.3mA, the zener diode is connected in series with a resistor on the voltage power supply. This is due to the fact that the zener voltage changes with the change in temperature.

An RL circuit is used in the circuit so that phase shifting can be achieved with the AC source where the inductor and resistor are connected in parallel. The position of toroid transformer may be found in the center close to front panel but far from the components to prevent interference. A suitable heatsink was used to compensate the heat dissipation and the circuit was placed on a casing with enough spacing.

The power supply can come from old PCs with enough fuses. A soft start circuit can be created by having a large resistor on transformer primary and relay.

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