I own a Acoustic 470 head. I moved it into a another room which is the jam room where we jam and what not. I noticed that i was getting a shock from my bass when i was playing one day and this has never been an issue before.
We later find out switching a switch on it stops the shock and the buzzing from the amp but I've switched this knob before and had it both ways in the other room and it's never shocked me. Is it an grounding issue in the amp? The other room had carpet so did that play a factor?
Here's a picture of the knob i switch (It's the GND/REV switch)
I've also checked it and it does it for both of my basses (So it's not a bass issue)