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In an amp with a 'typical' active, series, tube FX loop (CF Send and Gain Stage Return) the signal goes 'through' the Return jack internal connection when nothing is plugged into the Return. My question concerns the grounds when you do plug something into the loop. When you do...it seems that since the sleeve of the FX loop Send and Return cables are contacting both the Send and Return jacks (which are grounded)...that the entire FX loop chain is grounded in two places...which implies a ground loop to me. Is this true or am I missing something?
I do know that in one homebrew I had to wire one of the grounds (can't remember whether it was the Send or Return) to the 'switched' connection on a Marshall style jack such that when you plugged into it the ground connection was broken and the ground then went through the entire FX loop chain to the 'other' jack ground. Doing that eliminated a hum problem I was having when I used the loop (amp was fine with nothing in the loop). However, I've never used this amp to send signal to another piece of equipment...my setup here might cause a ton of hum if I tried (I don't know...just speculating).
Can anybody help me make sense of this? TIA!
I do know that in one homebrew I had to wire one of the grounds (can't remember whether it was the Send or Return) to the 'switched' connection on a Marshall style jack such that when you plugged into it the ground connection was broken and the ground then went through the entire FX loop chain to the 'other' jack ground. Doing that eliminated a hum problem I was having when I used the loop (amp was fine with nothing in the loop). However, I've never used this amp to send signal to another piece of equipment...my setup here might cause a ton of hum if I tried (I don't know...just speculating).
Can anybody help me make sense of this? TIA!