grounding pots

[scole]

does the body have to be grounded in order for the pots to operate?

[dai h.]

if the body of the pot is metal, you need to ground it or else you'll get a lot of noise. It will work w/out grounding but you'll get a lot of noise.

[Tom Phillips]

I'll add that the mechanical ground at the mounting collar is usually sufficient. As long as it is clean and tight. Common practice is to use a star lock washer between the pot and the chassis surface.

[soundmasterg]

If the pot is loose, and it is grounded only through the mechanical connection from tightening it up, then you can get intermittant popping and crackling with vibration like from a speaker. It is very hard to track down this type of noise sometimes, but it is easy to make sure all the pots are tight. Hoffman type builds use a ground buss bar soldered to the back of the pot casing to get around this problem. Not all pots can be soldered to though, and on his builds he also recommends to solder the circuit grounds to that buss bar. It seems to work ok, but I don't like it myself as it gives you multiple chassis grounding points, which you usually try to avoid. In my builds, I use Kevin O'Connor's galactic ground scheme, with a ground lift switch and isolated jacks. This method requires all circuit grounds to only touch the chassis at one point. What you do in practice is have little star grounds for each circuit area that all sum at one point near the ground lift switch and ground through a 51 ohm resistor and a cap (.01uf if I remember correctly). The resistor and cap suppress RF interference. You could still use a buss on the back of the pots but you would have to make sure all the circuit grounds ground elsewhere.

Greg