All grounds run with their own wire to the filter cap negative. Some things are tied together, like the volume pot's negative and the cathode circuit of the amplifier valves. All the RCA jacks are insulated from the chasis and are grounded to the volume pot as well. It could perhaps be described as a semi-star. Signal all gets tied to one and then on to the main negative of the flter cap. The chassis gets tied to the PS, and I try attaching the green line Ground with a clip lead to see if it helps or hurts the noise. Depending on the amp's grounding arangement, I suppose the main Ground lift might be a good thing to have on a switch....
regards,
Douglas

The Grounded Grid preamp that I breadboarded last month had a slight hum to it. It was grounded with a combination of star and bus technique and was technically correct. Finally got it quiet after much fiddling. The difference between hum and dead silence was moving one ground wire two inches along the ground bus. Just hope I can duplicate it when it comes time to transfer into an enclosure.

Gar.