I run sound for my church part time and also play bass with them on occasion. We did a restaurant gig a week or two ago and when plugging everything in I felt something that I was pretty certain was AC current coming from the rear of the Hartke 2500 head as I plugged in a tuner on the effect loop. It went away after about 10 seconds, but a bit later I felt it again on my strings. At the time I wasn't sure it it was current because I couldn't replicate it, so at the time I attributed it to nerve pain or something.
Sunday I'm running sound in our church, same amp is patched into the system, but is turned off. They're doing an acoustic set and the amp is hooked up to the direct out in the back and nothing is patched into it. On the board, the bass amp is showing signal and checking it through PFL I can hear a clear signal of our vocal monitor mix.
Again, I stress that the amp was not turned on. Nothing is plugged into the amp except the DI line to the board and the power to the wall. The signal goes away when I unplug the DI line or when I unplug the power cord to the amp. I eventually discover that the brass plate surround the receptacle where the monitors plug into on stage is touching the side of the L shaped TS plug. When I stopped it from grounding out, the signal stopped coming from the bass amp.
So my theory is that the monitor feed was shorting to the conduit and entering the building neutral/ground, somehow completing a circuit through the building electric. I'm not sure how it ended up passing through the Hartke, but that's where I'm wondering if it's possible for a grounding problem internally to allow a signal path like that, even when it's off. We have had problems with the tube pre amp that was not resolved by replacing the tube. The amp shares the same building ground as the rest of the system. The more troubling issue is that the current I thought I felt now seems more likely and a bit more dangerous. We've taken the amp out of service for now. Anyone have insight?
Sunday I'm running sound in our church, same amp is patched into the system, but is turned off. They're doing an acoustic set and the amp is hooked up to the direct out in the back and nothing is patched into it. On the board, the bass amp is showing signal and checking it through PFL I can hear a clear signal of our vocal monitor mix.
Again, I stress that the amp was not turned on. Nothing is plugged into the amp except the DI line to the board and the power to the wall. The signal goes away when I unplug the DI line or when I unplug the power cord to the amp. I eventually discover that the brass plate surround the receptacle where the monitors plug into on stage is touching the side of the L shaped TS plug. When I stopped it from grounding out, the signal stopped coming from the bass amp.
So my theory is that the monitor feed was shorting to the conduit and entering the building neutral/ground, somehow completing a circuit through the building electric. I'm not sure how it ended up passing through the Hartke, but that's where I'm wondering if it's possible for a grounding problem internally to allow a signal path like that, even when it's off. We have had problems with the tube pre amp that was not resolved by replacing the tube. The amp shares the same building ground as the rest of the system. The more troubling issue is that the current I thought I felt now seems more likely and a bit more dangerous. We've taken the amp out of service for now. Anyone have insight?