mesa boogie ground switch

[morbidalex666]

Hello there!!
I've just received my precious mark iv A (used) and I have this question: what does the ground switch do and how should I use it? It has 3 settings A - Off - B. Since the model is the A version and not the B, I can't get the correct manual from mesaboogie.com because they have only the later model's manual available for downloading. The B version doesn't have this switch.
Thanks

[52 Bill]

Hello there!!
I've just received my precious mark iv A (used) and I have this question: what does the ground switch do and how should I use it? It has 3 settings A - Off - B. Since the model is the A version and not the B, I can't get the correct manual from mesaboogie.com because they have only the later model's manual available for downloading. The B version doesn't have this switch.
Thanks

The ground switch connects either side of the AC line to the chassis through a capacitor. The center position disconnects the cap all together. As long as the AC cord has a three prong plug with a connected ground pin, just keep the switch set in the middle or off position.

[Enzo]

Its purpose is hum reduction. if your amp has any hum, try the three positions - ther is no "wrong" position. If one way hums less, set it there. Otherwise, set it in the off position. In most applications it won;t make any difference. Once in a blue moon it will be in some odd wiring circuimstance that it makes a small difference. As you found out, in later versions they didn;t even bother with it.