KT88 PP with Class-A/Class-AB switch

[pingfloid]

Do you know some PP schematic (KT88 or EL34) with a switch to easily conmute from A to AB class?
Thanks,
Manuel

 

[Sch3mat1c]

I'm not aware of anyone doing this. To do it properly would require changing the load impedance as well as bias and screen voltage.

You could run class A on the low side (say, the circuit normally calls for a 5k OPT - use 4k), then when you rebias it, run class AB on the high side (say it calls for 3k). In other words, since it's hard to switch the OPT, you make a compromise. You could use regulated screen supply and switch the voltage reference for the screen voltage switch.

Tim

 

[sajti]

I think it's possible to do, but this is only one way: You can rebias your class A amplifier to class AB, or B. But rebias the class B amp to class A is not good way. Class B amplifiers use higher plate voltage in most cases, so class A bias results overdissipation.
Just put switch into the bias power supply to get more nagetive voltage to the 1st grid. Very high -Ug results no current, which can be "standby" mode.

sajti