Electronics Australia Playmaster 300
300W Amplifier Module

An almost "stock" Playmaster 300W module; here the driver transistors have been mouted on a separate aluminium strip heatsink, rather than the main heatsink span.

The Playmaster 300 was a competing contemporary of the ETI466. It is impossible to know which was the more successful; I expect it was much the same between the two. The designs are however, as different as chalk and cheese. There are merits to both designs.

At first I was put off completely by the odd, central span location of the heatsink carrying the output transistors. So I preferred to stick with the ETI466's I was building at the time. Only later did I realise that the Playmaster 300 lent itself to having a fan blowing front to back (or vice versa) through the depth of the amplifier cabinet, down the length of the heatsink. I also later noticed the low profile of the Playmaster, and contrived to "stack" two, one upon the other, within a 3RU box, producing the highest power-to-RU ratio I ever achieved as an amateur constructor. The Playmaster 300 design has considerable merit!

The following files are available here; they're zipped .pdf's, with text and figures stored separately, to minimise file-size; - you sort of have to reassemble the articles yourself!

PartE.zip

"High Power Amplifiers"
Leo Simpson discusses the issues associated with high power amplifier design in Electronics Australia, October 1979, p.66-68.

Leo Simpson, formerly with Electronics Australia, now with Silicon Chip
PartA.zip

"300W Amplifier"
This introductory article by Richard Tymerski outlines some of the design theory underpinning the Playmaster 300, in Electronics Australia, May 1980, p.39~41

PartB.zip

"Playmaster 300W Amplifier"
John Clarke and Leo Simpson detail the complete amplifier module project in Electronics Australia, June 1980, p.54ff

John Clarke, formerly with Electronics Australia, now with Silicon Chip
PartC.zip

"Rack Mounting 300 Watt Amplifier"
John Clarke and Greg Swain detail how to fit the completed amplifier module into a rack mounting case, complete with power supply, fan cooling and a loudspeaker protection board, in Electronics Australia, July 1980, p.52ff

Greg Swain, formerly with Electronics Australia, now with Silicon Chip
PartD.zip

"Errata & Corrections"
Some pretty significant changes, in Electronics Australia, July 1980, p.100 and in Electronics Australia, August 1980, p.141