The ensemble R15, RV2, D5, T4, T5, R14 act as a current source.
VR1 act as offset adjustment.
My goal is to improve this amplifier to make it more convenient to put in service, removing the needs of manual trim pot adjustment and rather controlling the parameter with MCU (or otherwise).
I still have quite some issue into understanding how T8, T6 and T7 works to set the gate voltage.
I am looking for a solution to automatically set the bias current, controlled by a MCU that would adjust it at power-up and periodically while the amp is not in operation.
I also look to switch off the bias current completely when the amp is not active, to reduce power consumption and heat.
The concept is to replace this group:
By the following, allowing to control the current source from the MCU.
The MCU would also monitor the voltage across R32 during rest state to adjust the bias current. It can also stop any bias current during idle mode effectively disabling the amplifier.
Would that implementation make sense and would be possible to adjust the bias current by measuring across R21, as it is referenced to the ground it would be much easier.