Take electricity seriously

[Drummerboy2]

This had to have been an issue with the amp. The bass doesn't have any connection to AC power and electrical ground, except through the amplifier or any other powered device it gets plugged into.

It was really weird. He wasn't zapped bad but enough for him to feel it to the point he wanted to try another bass, changed basses to my bass and it was all good. I just swapped basses with him and let him use my good cable that was all I did. The power cord was the one it came with the amp and was good.

Like I said, it never happened before or after and I was the original owner of all the gear he played through except for his bass and cord he used that day. I was really puzzled by this, to the point I had the amp checked out by a really good local amp tech and he said it was all good.

I have heard other stories of bass players feeling the same thing when touching their strings. I have never experienced this myself.

Til this day I have never experienced this or know of anyone else other than that guy having this happened to them but have heard stories of the same thing a couple of times.

I'm trying to remember if there was a hum or buzz happening along with him feeling this on his bass. If I remember correctly that's one of the reasons I said try my bass. That went away too once he plugged my bass in.

 

[fdeck]

You can use one of these on your own gear, if any current goes through you and to ground it will trip, but only with your gear, PA mic is a different case.

https://www.amazon.com/TRC-Southwire-14650013-6-120-Volt-1800-Watts/dp/B000XU5MEG

You can also investigate microphone XLR connections and “ground lift”.

I’ve noticed a couple small new practice amps what I think are wired incorrectly inside the amp. They wired the fuse on the neutral side of the power transformer, then to the neutral wire of the power cord (US 120v wiring). If there is a short in the power transformer to ground, the fuse may blow, but the chassis could still be hot.

I've got one of these -- at least, it looks identical. I highlighted what you wrote about PA gear.

Note that I'm not an engineer or an electrician, but just a curious character. I took the device, plugged it in, and pressed the "test" button to trip it. Then I unplugged it and checked the connections with my ohmmeter. The "hot" and "neutral" contacts are disconnected, but the "ground" pin remains connected.

My interpretation is that if it senses a fault current, it will shut down whatever is plugged into it. But if the fault current is coming from somewhere else such as a PA mic or a different amp on stage, it will still be able to flow through you even if the device has tripped.

I have a rule that I don't trust anybody else's gear on stage.

 

[agedhorse]

It is not legal to disconnect the ground.

 

[Drummerboy2]

It is not legal to disconnect the ground.

And I see so many people doing this! The Ground is there for a reason.

 

[fdeck]

It is not legal to disconnect the ground.

Thanks. It's worth re-iterating that I was just trying to understand how the thing works, what it protects, and what it doesn't protect. I'm not smart enough to think of a way to protect everybody on a stage where different things are plugged into different circuits, unless every circuit is on the same GFCI. And even then, it takes a real engineer to analyze all of the possible fault conditions.

In the meantime I don't touch anybody else's gear.

 

[Bertr]

It is not legal to disconnect the ground.

The suits have right this time...

One thing that happened to me once in the 90´s:
In France, large public venue from the late 70's (so well grounded),l arge stage, plenty of lights.
I was playing guitar on a stock Marshall valvestate (with ground).

I got a small zap from a SM58 on my lips. Once (I may have touched it again, in any case it happened just once).
We were the first band and the stage had been ready for a couple of hours. The set up was done by pros so I assume all power had a ground connected. Now that puzzled me.

I thought maybe the '1' of the XLR cable of the SM58 was broken somewhere between the desk and the mic.
The mic might have risen in potential due to its case not being grounded anymore.

I'm still puzzled. Andy, what do think?

 

[byacey]

This might have simply been static discharge. If the mic had pin one disconnected, it shouldn't be a shock hazard at all.

 

[byacey]

Thanks. It's worth re-iterating that I was just trying to understand how the thing works, what it protects, and what it doesn't protect. I'm not smart enough to think of a way to protect everybody on a stage where different things are plugged into different circuits, unless every circuit is on the same GFCI. And even then, it takes a real engineer to analyze all of the possible fault conditions.

In the meantime I don't touch anybody else's gear.

The sound production company is responsible to ensure all their gear is properly connected and grounded, as well as ensuring the same for the AC drops on the stage for the musicians back line gear. The problem is when the musicians bring in their own gear, you don't know what state the gear is in, if their cabling is all in good order, and properly connected. I've seen some questionable things that appeared to be home-handyman cobbled together; things like this I try and discourage from being brought onto stage.

 

[byacey]

I've got one of these -- at least, it looks identical. I highlighted what you wrote about PA gear.

Note that I'm not an engineer or an electrician, but just a curious character. I took the device, plugged it in, and pressed the "test" button to trip it. Then I unplugged it and checked the connections with my ohmmeter. The "hot" and "neutral" contacts are disconnected, but the "ground" pin remains connected.

My interpretation is that if it senses a fault current, it will shut down whatever is plugged into it. But if the fault current is coming from somewhere else such as a PA mic or a different amp on stage, it will still be able to flow through you even if the device has tripped.

I have a rule that I don't trust anybody else's gear on stage.

Ideally, a solution would be to have a separate ground fault protected outlet for every stage drop. This would only trip and disable the device(s) plugged locally into that outlet, without disrupting everything on the stage.

 

[fdeck]

The sound production company is responsible to ensure all their gear is properly connected and grounded, as well as ensuring the same for the AC drops on the stage for the musicians back line gear. The problem is when the musicians bring in their own gear, you don't know what state the gear is in, if their cabling is all in good order, and properly connected. I've seen some questionable things that appeared to be home-handyman cobbled together; things like this I try and discourage from being brought onto stage.

What is this sound production company of which you speak?

Jazz gigs tend to be "anything goes." You can tell the year that someone started their first band, from the age of their PA system. A lot of the stuff I've seen gives me the heebie jeebies. Fortunately, there's very little reason for anything being interconnected.

 

[byacey]

What is this sound production company of which you speak?

Jazz gigs tend to be "anything goes." You can tell the year that someone started their first band, from the age of their PA system. A lot of the stuff I've seen gives me the heebie jeebies. Fortunately, there's very little reason for anything being interconnected.

Actually, the more stuff interconnected, the better the chance of everything being grounded, even if just through the audio cables, should one of the AC cable have a lifted or broken ground.

 

[BlueTalon]

The more I read stuff like this, the better I feel about my decision to go wireless with my bass. In fact, I like that decision so much, I decided to get a wireless vocal mic as well.

 

[agedhorse]

The suits have right this time...

One thing that happened to me once in the 90´s:
In France, large public venue from the late 70's (so well grounded),l arge stage, plenty of lights.
I was playing guitar on a stock Marshall valvestate (with ground).

I got a small zap from a SM58 on my lips. Once (I may have touched it again, in any case it happened just once).
We were the first band and the stage had been ready for a couple of hours. The set up was done by pros so I assume all power had a ground connected. Now that puzzled me.

I thought maybe the '1' of the XLR cable of the SM58 was broken somewhere between the desk and the mic.
The mic might have risen in potential due to its case not being grounded anymore.

I'm still puzzled. Andy, what do think?

Hard to say.

 

[bdplaid]

 

[Spectrum]

The more I read stuff like this, the better I feel about my decision to go wireless with my bass. In fact, I like that decision so much, I decided to get a wireless vocal mic as well.

I get what you're saying, but if you spend all your time reading about crime and bad weather you might never leave the house either. I hold that if your gear is taken care of properly and you are mindful of hazards there's no reason to fear simply plugging into an amp and playing.

Car crashes kill more people than faulty guitar amps (I think, anyway, wouldn't that be something if the reverse were true?) but we still drive to gigs.

 

[BlueTalon]

I get what you're saying, but if you spend all your time reading about crime and bad weather you might never leave the house either. I hold that if your gear is taken care of properly and you are mindful of hazards there's no reason to fear simply plugging into an amp and playing.

Car crashes kill more people than faulty guitar amps (I think, anyway, wouldn't that be something if the reverse were true?) but we still drive to gigs.

I don't think the analogy works. I buy insurance for my car, but that doesn't mean I'll necessarily ever be in an accident. It's quite possible that I could go through the entire rest of my life playing with a cord connecting my bass and my mic, and never have a shock incident again. But I have had them in the past, and I'd rather just spend the money and not have to worry about it in the future. Wireless is just another form of insurance.