Wharfedale Pro PM 600 Transformer

The Wharfedale Pro 600 transformer provides power for three main systems of this amplifier; hence there are three dedicated bridge rectifiers in the design. One set of windings on the secondary side establish a split-rail power supply for the main power amplifier. Another set of windings establish another split-rail power supply for the preamplifier and mixer panel. A final pair of windings establishes a single rail supply for the internal cooling fan.

The iron core transformer contributes to most of the weight, and it mounts on a steel bracket and looks impressive.

I measured the voltages on the red-blue-red group of wires on the secondary side of the transformer, and the red wires carry 47 V AC with respect to the centre tapping, which is the blue wire.

The yellow pair of wires carries 38.3 V AC, which rectifies into positive and negative DC currents, and then a pair of voltage regulators establishes regulated ±15 V rails. The operational amplifier circuitry on the mixer PCB uses this voltage. The white pair carries 12.8 V AC, and this is rectified and used to power the internal cooling fan.

As you can see, here is my split-rail 15 V power supply circuit installed. This circuit powers the mixer panel and therefore I am able to use the mixer functions, without the power amplifier.

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