Transistor biasing

[richeros]

I was reading about valves vs. transistor on the Elliot Sound pages when I saw this
"The power amp has an ingenious system for optimising grid bias of each output valve, which contributes to minimum distortions and increased valve life. A pair of light-emitting diodes (LEDs) and a screwdriver-operated potentiometer associated with each valve is fitted to the front panel and adjusting the potentiometer for equal light intensity from both LEDs (of the pair) provides correct grid bias voltage. Level controls are fitted for each channel."

So I was thinking, can't the same be done with output transistors/MOS-FET?? Not necessarily LED's....... Instead of matching we could adjust a base transistor or the the individual signal level for each O/P-device. Anyone have some info om this??

Richard
NORWAY

 

[HarryHaller]

Bias adjustment

Most solid state amps have a pot to adjust to output stage bias
once it is set it doesn't move much after the amp is warmed up.
Tubes require frequent bias adjustment due to varying AC voltage, tube aging, and people swapping tubes for what ever reason. Push pull tube out but stages must be baised just right to
prevent dc currents in output transformers. Kind of a hassel for some people.....

H.H.