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Need help - getting small shocks from my mic

jcburn

jcburn

Oct 11, 2003
2,628
1,674
53
Tasmania, Australia.
everburn.com.au
#1
Hey everyone - have started this here as this could be an amp issue but if there is a better spot please suggest.
For my last three gigs I have been getting small shocks through my microphone.It is bareable but painful and annoying and is constantly there(it's not intermittent). I realise that no one here will be able to diagnose this problem but any heads up as to what the problem may be would be appreciated.
This is my signal chain. Bass - Fender stomp tuner - MXR M80 - Hartke LH500 - Hartke VX410. Microphone (Shure SM58 Beta) into Yamaha PA to Yamaha passive speakers.
Without touching my bass I get no shock - it is only when the bass is plugged in and I'm touching it(the strings specifically).
Here is the troubleshooting I've done. Have plugged directly into amp and problem is still there. I originally thought the problem was the mic but the problem is present no matter what mic is used, it seems to engage only when touching the bass. It also seems if I grab the mic and touch the strings with my hand the shock then appears through the strings.
Could anyone suggest what the problem might be? Bad ground in the bass, amp?
 
#3
Am I correct that the only things plugged into the wall are the Hartke bass head and the Yamaha PA? Either of those could have a faulty ground. Another possibility is faulty wiring of your outlets.

This is dangerous. Don't use your body as test equipment. Don't use this gear until you find out what's wrong and have it restored to safe working order by a knowledgeable tech.
 
#5
Common problem back in the day of ungrounded equipment and polarity switches.
I've seen a guy draw a blue arc from the mic to his lips more than once.
Also had a friend grab a mic while holding his bass strings and was nearly electrocuted; quick thinking and a full running body tackle from the harp player helped to free him although he had to have knee surgery and has walked with a limp for the last 25 years.

A volt meter between the strings and the mic will tell you how much voltage but what will kill you is the current.
A good amp tech can fix your set up.
While we sometimes joke about "being shocked by God due to bad playing / singing", line voltage electricity with 15 amps behind it is nothing to play with IMO.
 
#7
Back in the day, that used to happen all the time whether it was a mic, mic stand or guitarist. Steve Martin used to do a gag based on it by grabbing the mic stand and flailing around like he was being electrocuted.

If you wanted to grab someone's attention (or let them know they messed up) you'd touch their neck or ear with your finger. It was like a static shock on steroids. Was always worse if you weren't expecting it or on a sensitive area like the face or neck.

Like they said, it's all about the grounding.
 
#8
I sometimes had this happen at a club with poorly wired outlets as well. If there is a ground failure in the outlet causing this, no proper equipment solution will fix it. So I bought a wireless. Eliminates (or minimized) my body as a ground path and the mic stopped biting me.

But make sure your equipment is properly grounded as well.
 
#9
Just because you are getting the shock doesn't mean i's not the other guys gear / pa thats at fault, quite the reverse...
If someone else has a bad earth or has taken the earth out (usually the guitarist) you get the shock because you are earthed. PAT test all the gear and be careful guys have died as a result of bad earth / mic
 
#10
Small shocks may seem like a small problem but what their existence means is that you have little if any protection from electrical malfunctions. Should your amp or the PA fail, you will get a lot bigger shock. And remember this; large current will indeed fry you but even small current can cause lethal heart failure. Electricity is dangerous enough even when properly grounded so don't risk it.
 
#13
From what you're saying, the bass seems to be grounded correctly, but when you are touching ground (the strings) current flows to ground through you. Not bad if you want to be a conductor... (rim shot!). It could be something simple like your mic cord, but the best thing to do is always play wireless - or stay away from the mic. That way you don't have to worry. I always carry a circuit tester in my gig-bag, which I use before plugging into any venue's AC outlets. Then I can give a head's up to everybody about what's what in the power supply. Sometimes one outlet will be good and the other faulty (Hot and ground reversed, NO ground, + and - reversed - I've seen all of these. If you plug your bass rig into a good outlet, and the PA is plugged into a faulty outlet, you will get shocked. So your best bet to deal with it is a good wireless, which also does away with the hum you get from bad grounds.
JMHO and YMMV, but I hope this helps.
 
#14
I have an old old tube amp with a 2-prong cord and it does this very predictably.

I should wire it for proper ground. It's been on my to-do list for a decade. But the amp is very low power, pleasantly warm sounding but not quite loud enough for a big bedroom.

For the OP's amp, if it's getting used out I really think you need to get it checked out before using.
 
#15
Get all the gear checked out. Switching to wireless works until the day you take the mic off the stand for whatever reason and walk over to your rig to adjust it while holding the mic. Use a tester on the outlets. Problems like this are rare with modern gear, but small shocks tell you that you're 99% of the way to getting big, dangerous shocks. Please get your gear checked.
 
#17
Ahhh ... reminds me of the "Old Days".. trying to figure which way to throw the ground switch. I dont miss those lip biting shocks off the microphone. I used to tap the guitard player in the bare arm with one of my tuning pegs to piss him off.
 
#18
jcburn said:
Hey everyone - have started this here as this could be an amp issue but if there is a better spot please suggest.
For my last three gigs I have been getting small shocks through my microphone.It is bareable but painful and annoying and is constantly there(it's not intermittent). I realise that no one here will be able to diagnose this problem but any heads up as to what the problem may be would be appreciated.
This is my signal chain. Bass - Fender stomp tuner - MXR M80 - Hartke LH500 - Hartke VX410. Microphone (Shure SM58 Beta) into Yamaha PA to Yamaha passive speakers.
Without touching my bass I get no shock - it is only when the bass is plugged in and I'm touching it(the strings specifically).
Here is the troubleshooting I've done. Have plugged directly into amp and problem is still there. I originally thought the problem was the mic but the problem is present no matter what mic is used, it seems to engage only when touching the bass. It also seems if I grab the mic and touch the strings with my hand the shock then appears through the strings.
Could anyone suggest what the problem might be? Bad ground in the bass, amp?
Click to expand...

The PA is on a different circuit than your amp - and one of the two circuits has the hot and neutral wire reversed.

It's quite likely one or the other also either has a bad safety ground, or someone has cut the safety ground off some plugs.

I'd advise a circuit tester and fixing the problem before using it again - people have been killed by this problem.
 
#19
Circuit tester is a nice tool but not good enough unless all outlets are tested (entire back line & PA system)
It also only tests for L1 and neutral reversal or an open ground
Voltmeter is the best tool IMO
 
#20
This happened to me when a power strip cord developed a fault in its third-prong ground. This situation can kill you; it has killed others.

Get a cheap outlet tester and check your power strips first. Then wall outlets. If you don't see a fault on those, then have amp and PA checked.

A voltmeter will probably show about 60v between the mic and your strings; this is a sure sign of potential electrocution.

Photo: Typical outlet tester, under $10, available at hardware stores and Home Depot.
 

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