I have seen so many tube guitar amps purposely ground lifted. I have traveled the world with work boxes stocked with ground pin lifts for AC power. I won't let anyone use them if I'm around. It's so dangerous. One time, in Colombia, I was measuring power from a generator. I kept getting 14 volts between ground and neutral. I asked them to see the generator tie in because I knew something was wrong. The ground was disconnected in the generator and when I asked them why they said "Because the PA system was buzzing and it stopped when we did this". The PA was on and being tuned during this so there were thousands of watts running (it was an arena show) and the entire system had no ground. I made them change the generator out. This is one of many stories like this.
Sadly, I'm no longer amazed to hear of what happens to musicians' electronics and power. When in broadcast, we had standing instructions that all musicians' kit had to be PAT tested before it came into the (TV) studio. Anything faintly dubious was to be powered via an isolating transformer. Or rejected. But I've seen far worse with building labourers. No wonder battery tools have been promoted.
Absolutely!
Dealt with many musicians - and the "techs" they used. DJs were almost as bad. However these days (post about 1985) the "high end" upgrade folks are pretty horrible too. Today it is just plain scary out there.
Dealt with many musicians - and the "techs" they used. DJs were almost as bad. However these days (post about 1985) the "high end" upgrade folks are pretty horrible too. Today it is just plain scary out there.
Most mics have pin 1 connected to the case both for safety and for shielding.
There should be no voltage between a microphone case and earth ground.
Your guitar ground "ring" is connected to the strings to reduce noise, and should have virtually no voltage to earth ground.
There never should be more than a few volts potential between guitar ground and PA ground.
No, not normal at all.
Are you sure it was AC, not DC voltage?
I suspect you may be reading phantom power between dropping resistors, due to the mixer not connecting Pin 2, and applying phantom power between pin 1 and 3, as this Phonic block diagram appears to show:
Years ago, I purchased some Phonic microphones from a Parts Express buyout at a "too good to be true" price, something like $16 for four mics with 3 meter cords.
The Phonic mics worked with the supplied cord into a guitar amp.
However, they were wired with the dynamic element between pin 1 and 3, rather than 2 and 3, so would not work plugged into a normal mixer XLR. I swapped the wire from pin 1 to 2, the mic then would work plugged into a standard XLR.
The molded XLR to 1/4" TS cords were was also miswired, and had nothing connected to pin 2, making them useless after I corrected the microphone wiring.
After correcting the microphone pin 1/2 swap, I found they were out of the normal polarity convention of pin 3+, pin 2-, so had to rewire that mistake also.
Anyway, wouldn't surprise me to find a Phonic product miswired.
Good luck!
Art
Phantom power should never be more than 48vdc. In many devices phantom power is actually lower voltage than the official standard of 48v. Some devices produce phantom power as low as 12vdc.