A75 Class A MOSFET Power Amplifier Front End Board

The A75 amplifier is a 1992 design by Nelson Pass and Norman Thagard (a former NASA astronaut, no less!).

The front end provides up to 90V peak-to-peak output with low distortion. It is designed to drive 12 pairs of IRF230/IRP9231 MOSFETs - today, six pairs of IRFP240/IRFP9240 will provide similar characteristics.

• Class A audio power amplifier.
• Designed by Nelson Pass and Norman Thagard.
• 75 Watts per channel.
  
• All through hole, easy to assemble.
• One board carries front ends for two channels.
• The board closely follows the published design.
• The output stage (MOSFET transistors and their source resistors) needs to be assembled off board.

References:

• The original article by Nelson Pass: Part 1 and Part 2