Wharfedale Pro PM 600

The PM 600 was a professional-class powered mixer amplifier system manufactured in 2002 by the Huntingdon based Wharfedale Company. This amplifier provides 230-watts output into a 4 ohm speaker coil. The mixer has five inputs for microphones, and six inputs for line channels. Each input channel has a 2-band equaliser for high and low frequencies. There is also an additional 3 band master equaliser that can further boost or cut these frequencies. The speaker outputs are through ¼-inch jack sockets, and there are two of these sockets, which allow two speakers to connect in parallel. This amplifier has a cooling fan within the case, which remains powered all the time.

The amplifier power output design is symmetrical push-pull type consisting of a complementary pair of transistors; 2SC3856, and 2SA1492. As you can see, they use a double pair connected in parallel to produce a high-current speaker driver. Each transistor has a 0.33-ohm resistor (R731, R731A, R730, R730A) in the current path, hence if a transistor goes short, then its respective resistor will burn and go open.

Each channel has an input through XLR, plus ¼-inch jack sockets. There are controls for the volume, high band, low band, and EFX level. For more information, please consult the product documentation. There were two versions in the series, and the prior version was the PM 500 which looks similar but could provide only 120-watts output. It had inputs for four microphones, and five line channels.

Mixer system Front Panel

The master equalizer has a high control (12 kHz), mid control (1 kHz), and low control (80 Hz).

In the following sections of this multi-page article, you can see photographs of the insides of this amplifier, the original PCB, my amplifier rebuild, and the power supply section.

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