Lip Shock

clinton

So I mentioned that I just got a AC15C1 greenback loaded Vox.Well last night about 5 songs into band practise and all of a sudden I start to get shocked on my lips from the mic while holding the guitar strings.

Thought that maybe the power cord was faulty so I swapped it out for another one but the shocking still remained. So it looks like it must be something inside the amp. It was all fine and then all of a sudden it just started shocking my lips on the mic. I landed up going back to my Tonelab and pluggging into the pa system (with a big difference in cut through tone)

Anyone have any ideas as to what it could be?

The hack with this situation is that I have a gig this Saturday and next Saturday.

AlanRatcliffe

There is a difference in ground potential between your amp and whatever the mic is connected to. Make sure all the gear is plugged into the same power source and if that doesn't cure it, you'll have to track down the culprit. It could just as easily be the mixer or power amp as it could your guitar amp.

DonovanB

I've had that plenty times. It is more likely the PA loop than your guitar gear.

Get one of those sponge mic covers, it prevents the shock but doesn't solve the actual problem.

clinton

The thing that made me think something could have malfunctioned is that it only started shocking me halfway through the set.
I will do another test here at home and see.

The PA and my vox and the passive mixer are all plugged into the same powerpoint in our band room (else we get serious ground hum)

Question: is it possible that this could be caused by something malfunctioning in the vox? And what would it be.

Bob-Dubery

What's your pedalboard plugged into?

It seems to me that even if the PA and the guitar amp have the same earth, but the pedalboard is connected to something else that you have the possibility of a ground loop and resulting difference in potential.

clinton

everything plugged into one power point.

When I took the vox out of the equation and just connected my tonelab to the PA direct the shocking stopped.

SETUPS:
shocking setup:- GUITAR: guitar - tonelab(amp sims off)- Amp / VOCALS: vocal mic-mixer-poweramp (all plugged into one socket)
non shocking setup:- GUITAR: guitar-tonelab(amp sims on)-mixer-poweramp / VOCALS: vocal mic-mixer-poweramp (all plugged into one socket)

TomCat

+1 to what Alan Said.

If you have a multimeter, measure the neutral/earth voltage on all your kettle plugs. You might have lost a ground somewhere. The voltage should be no more than about 0.5VAC. If you fine one much higher, say 30volts or more then that will be the culprit.

Very Important....check that the AC-15 power plug has the ground wire connected.

Gearhead

The amp being faulty is a more remote possibility, but it should be easy to test. Switch the amp on and measure between the input jack (outside of hole / on nut) and the earth of the socket next to the one you are plugging into. Put the multimeter on AC but also on DC.

FruitarGeek

I have the exact same problem, my remedy however is...

a sock! as long as its clean it will hide the problem (much like the sponge)

Sean

FruitarGeek wrote I have the exact same problem, my remedy however is...

a sock! as long as its clean it will hide the problem (much like the sponge)

LOL
Don't know what is more amazing, the fact that you do that, or the fact that you share that openly thinking it's a great idea ??? ?

You're not worried about how that looks? You know, having a sock pulled over your mic? ??? Do you ever gig like that? ?

FruitarGeek

Well no, I only seem to get the shock at my bandroom, live situations the mic is fine. But I dont have those sponges thats why I have to use a sock.

clinton

Thanks for all the info guys.... played a gig last night and took the amp with me, it was an outside gig and it was pouring with rain ?. Plugged everything in, said a prayer, and stepped up to the mic........NOTHING. What a relief, seems that the ground loop must be in our band room.

Must say the AC15C1 was superb on the night, managed to get such creamy tones for bluesy solos and also got some searing wah lead tones for Foxy Lady.
Our U2 stuff sounded unreal.

I love this amp and cant wait for the Greenback to be fully broken in.

Next week we have a much mellower gig where I will test the amps jazz and blues tones (cant wait)

Gearhead

Just to set the record straight - when shocked it is not a loop, but a lack of ground. Ground loops are caused by connecting to ground through two or more ways and they just make hum. Think of ground like branches on a tree:
- no branch floats in mid air (= always make sure you connect to ground one way)
- branches split and split but do not connect back to each other (= always make sure you connect to ground only one way)