Microphones - getting shocked by mics

[KProductions]

Hi All,....

I have an active system setup in a local venue. Tonight, - a couple of the artists reported being "shocked" by the vocal mics (beta 58's). I've had the same setup in the same location for the last 6 months and today was the first time that anybody ever reported any issue.

I have the console (Mackie VLZ 24-4) ground lifted, as are my rack, the speakers, and monitors (to eliminate hum).

The guitar amps were plugged directly into a 4 outlet surge box, - which was plugged directly into the wall (grounded)

Any suggestions...???

Thanks

[rroten]

When you say ground lifted, do you mean the signal ground or power ground? I must strongly insist that electrical grounds should never be lifted. NO EXCEPTIONS! I don't want to sound mean, but this is safety we're talking about. Please make sure that all of your equipment is using all 3 prongs on the electrical connectors.

Ryan

[DaveySimps]

Never lift the ground on your racks, or any other electrical gear. It is a serious safety concern, and strong possibility of what is causing your problem. I know it is a PITA, but find out what is causing the hum instead of taking the easy and unsafe way out of it. You system will be better for it.

~Dave

[Eboy87]

Never lift the electrical ground!

If you have hums and buzzes, there are other solutions that aren't life threatening. Lifting the ground on your gear is what caused the artists to get zapped. Since the gear wasn't grounded, but the amps were, the path to ground was through pin one on the mic lines, through the metal mic, across the artists' lips to their grounded amps. This is not a good thing!!!!! I cannot stress this enough, don't lift the AC ground on gear!!

[Erwin]

I had the same problem once.

We had nothing ground lifted. The problem seemed to be a faulty power bar. When we replaced it, the problem went away.

I have also been told that having a power conditioner for band gear can help. It is said that a badly wired guitar amp mixed with an ungrounded Mic can be lethal for a performer.

If you google shock from Microphone, you will find many horror stories, things to avoid, but no solutions. It is however, how I learned methods to get rid of performers

Seriously though, it is probably a problem with a ground connection in you system. Either the amp or the console.

[Eboy87]

Originally Posted by Erwin

It is said that a badly wired guitar amp mixed with an ungrounded Mic can be lethal for a performer.

As a guitar player, what happens is this. Usually these stories deal with tube amps. Voltages inside tube amps can be up to 300 volts, and if there's a problem, that goes to ground. It just so happens, the strings of a guitar are also connected ground (usually). If the ground is lifted on the amp where it's plugged into the wall, that voltage winds up on the strings, as you are now the path of least resistance to ground. And once you get close enough to a mic connected to a grounded sound system, you complete the circuit. People can (and have) die from this.

Please, throw away all ground lifts.

[KProductions]

thanks,... so

1. How come this just came up tonight after 6 months and many other shows...??

2. How do I eliminate the hum if I don't ground lift the system...?

All your advice is appreciated.

[Erwin]

1. Things have to break sometime. Ask this instead. Why not now?

2. The hum is being caused by a faulty and/or improperly installed piece of kit. It can take a lot of work to isolate it. You need to start eliminating suspects by removing them from the system one at a time.

Someone with more expertise can likely give you a good place to start. Dirty power and bad cabling would be my first guesses.

[dvsDave]

1) Ground everything

2) only test one variable at a time. To save time, I start with the mic and move back along the signal path.

[BillESC]

1. All of your gear should be grounded.

2. All audio should be on the same electrical phase.

Problem more than likely solved (unless there is a defect in one of your components.)