Bias Eden amps?

[Axtman]

Does anyone know how to adjust the bias in Eden amps?

Also what is the purpose of LED1 and LED2 in the circuit?

Schematic: WT550 - Schematics (2003).pdf

[Jazz P Bass]

Part of page 3 & page 4 states to set the bias across the emitter resistors at 4 mv's.using Trim 1.

[teemuk]

LED1 & LED2: The first evident task of these is generating voltage potential across TRIM3 equivalent to two LED forward voltage drops. TRIM3 is "zero adjust" for the input differential stage and used to nullify any tiny DC offsets resulting from imperfect transistor matching. The adjustment range is between about +/- 1.8VDC, well enough to nullify few millivolts of offset.

For the second task I'm throwing an educated guess: The LED2 provides a fixed voltage input to base of Q2 mounted to heatsink to sense temperature. Base-emitter voltage of Q2 varies with temperature (it decreases at higher temperatures) and when VBE falls below threshold set by TRIM2 the transistor triggers the FET-based mute circuit of power amp's input signal.