Possible reasons for electric shock

[Bluefinger]

While plaing a gig yesterday I had some electric shocks when touching the Guitar and the mic at the same tim. It was not the full 220 volts but still a bit unpleasant or at least scary. It was definitely AC since I could feel the AC hum.
Here's how we were plugged in:
The PA was connected to one wall socked. My amp was plugged into another socket at the other end of the stage. The bass player was plugged into the same set of sockets as I and he had a decent amount of hum in his solid state amp but did not feel any electric shocks. The chassis of my amp is propperly grounded. I can'r recall the exact reading but the resistance from the guitar bridge to the ac plug's ground connector is a couple of ohms. Can't speak for the bass amp.
Are there any other possible reasons for this than maybe a leaking filter cap in my amp or a grounding problem in the club where we played?

thx!
BF

[R.G.]

While plaing a gig yesterday I had some electric shocks when touching the Guitar and the mic at the same tim. It was not the full 220 volts but still a bit unpleasant or at least scary. It was definitely AC since I could feel the AC hum.

Definitely not a pleasant feeling!

Are there any other possible reasons for this than maybe a leaking filter cap in my amp or a grounding problem in the club where we played?

The club wiring is a big possibility, especially since the PA (which is what I read as the real issue here) was on another branch of the AC power, I think, from your description.

Leaking filter cap is not a cause, if you mean the DC filter caps in the amps. However, if any of the amps involved have a "death cap" and a two-wire power cord, they may be the problem. Your amp, with a proper third wire ground, is most likely to be set up correctly. Your bass player's amp may or may not be. But I think it's the PA that's leaking AC, and your properly grounded amp is making you a target.

It is also possible that the club's power wiring has a high impedance third wire ground.

I recommend this for all players who work in places using other people's electrical power: Get one of those plug-in safety testers. You're not in the USA, I'm guessing because of the reference to "220Vac", but the equivalent must exist in your country. These testers are plugs with no power cord that just plug into the wall socket and have three LEDs that light up to tell you if the power is wired correctly in the plug. They're about US$5 here. I recommend every player have one in the gig bag and take responsibility for testing the AC socket their amp plugs into. An open safety ground or reverse polarity socket can fry you.

Another thing you can do is to buy a cheap Digital Multi-Meter and test the voltage from your guitar strings to the microphone and mike stand. Here in the USA, these can be had for as little as US$5 as well. The cheapest DMM will work. Set it to AC volts on the range that fits your local AC power voltage and probe your guitar strings and the microphone. Anything over about 20Vac will be very unpleasant, and full line voltage may be deadly.

It is possible to rewire a guitar to make you more immune. The reason strings are grounded is to avoid hum. However, they do not need to be solidly grounded. There is a wire from the bridge of your guitar to the signal ground on the jack. You can find that wire, cut it, and insert a 100K to 220K resistor paralleled with a 0.01uF/1kV ceramic disk capacitor and get good hum immunity, as well as not being killed by the current if the microphone is live. You'll still feel the current, but it won't be as deadly because of the high resistance to AC ground you've inserted.

The PA was connected to one wall socked. My amp was plugged into another socket at the other end of the stage.

I'm guessing that either the club AC wiring caused this, or the PA has an AC leak. You might want to test the PA by checking the AC voltage from the microphone shell to powerline AC ground with a DMM again. This should be dead zero. If it's not, there is an AC leak in the PA. If it is dead zero, unplug the PA and check continuity/resistance from microphone shell to the ground pin on the AC power cord. Should be zero ohms. You do not want to do the resistor/cap trick on the microphone. This should be solidly grounded.

[Bluefinger]

Thanks! I won't be there anytime soon but I contacted them and let them know that they should check their stuff, just to make sure.

all the best
BF

[jrfrond]

Never trust house wiring. The aforementioned AC Tester is a MUST-HAVE for every gigging musician, sound company, and anyone else who plugs anything into a wall socket. Hey, I got knocked on my ass in my own house when I first moved in by touching the kitchen sink and the refrigerator at the same time! Turns out that the previous owner was a REAL amateur electrician. Unfortunately, some alleged pro's are amateurs as well.

You got lucky. More than a few people have been cooked in the same manner, and 220V has even less of a sense of humor than 110V!

[Phostenix]

... and 220V has even less of a sense of humor than 110V!

I still find it hard to believe that countries give 220v to consumers. I probably wouldn't have made it to 10 years old with that.

[Jazz P Bass]

I still find it hard to believe that countries give 220v to consumers. I probably wouldn't have made it to 10 years old with that.

Yeah, but in this day & age of Green Everything, who is going to argue.
Most mains services to USA households are 220-240Vac.

[Steve Conner]

It's worse than that, on the Continent they get 400V, 3 phase to their homes. Big appliances like electric stoves and water heaters run off it. Crazy Europeans.

I survived a childhood of 240V outlets, with a few REALLY nasty surprises.

[Enzo]

Agreeing with the others, get the simple outlet tester. Check your stage outlets, but also go up to the PA booth and check theirs. And their distribution as well. Just because a wall outlet is properly grounded doesn;t mean all those outlet strips you use to plug everything into are 100%. Test their outlets as well.

[Phostenix]

Most mains services to USA households are 220-240Vac.

Sure, but most users don't go in there.

[R.G.]

Most mains services to USA households are 220-240Vac.

It is brought in as two halves of a balanced 240Vac, giving 120Vac nominal on each side of neutral. So most wall sockets are 120Vac with respect to ground/neutral. This allows a new problem if the neutral going back to the pole is high impedance. If that happens, a heavy load on one half of the split 240VAC unbalances the two halves, and one half may have only 70-80V while the other rises to 160-180Vac. Makes for some interesting problems.

[Enzo]

Interesting problems that probably won't be there when some one comes out to check.

[Phostenix]

We had something like that happen in our computer room at work a while back. The building is 3 phase whatever voltage, so it's not quite the same, but one of the circuits feeding a rack dropped to about 80v, making the servers very unhappy. Electricians had to replace a cooked neutral. They figured it out pretty quickly. Not their first rodeo, I guess.