[Amps] CW & SSB amp

[Steve Flood]

I'm planning a 3x813 amp in grounded-grid.  Primary use will be for 160-80-40-20 CW (Class C).  What must I do if I occasionally wish to run the amp in linear SSB service (Class B or AB)?  Am I understanding correctly from my reading that I need to add an adjustable grid bias voltage control for adjusting cutoff,  and an adjustable plate voltage control (variac?).  It seems like some amps use one way or the other but not both.

steve
kk7uv