Passlabs Amplifier Projects

This was built on a "without compromise" approach. The circuit boards were made with the help of the electronics workshop at the University of Adelaide. Dual power supplies were used, the chassis was custom made and powder-coated, and high quality components were used throughout.

The result was that this was not a cheap amplifier to build. Total cost was in excess of $1000 (AUS) but this is actually very competitive given the cost of comparable commercial amplifiers.

For the dozens of folks who have asked about substitution parts, Nelson has now answered this himself (link). I initially used NTE substitutes (NTE-251 and NTE-252) and these worked fine. I had a catastrophic failure some time ago and wound up replacing the output devices (though it turns-out they were actually fine !!!).

For the replacement I used some Motorola units with higher power rating: Motorola MJ11015 & MJ11016.

There was no discernable performance difference between these devices and the amp is still working fine. The cause for the "failure" was in fact a static "zap" overloading the input and damaging the differential input pair. I have incorporated some simple protection as 2 "back-to-back" 6V zener diodes across the input, as suggested by Nelson.

If you want I have positive images for the circuit boards which are a little neater than those in the article. (Scale these to 300dpi for correct size)

Overall it is a very nice amplifier, you will not be disappointed if you take the trouble to build one !