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I get a buzzing noise from my guitar when idle. However, when I touch the strings or touch any metal parts (strings, bridge or the metal portion near the output jack), the noise goes away completely. What is the reason for this and how can I completely eliminate this.

I understand it may be grounding issue. I am connecting my guitar to a roland cube20xl amp. I tried with a different guitar and the noise was much lesser. Could something be wrong in my guitar?

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Are you using only single coil pick ups? Do you have the option of trying the same amp with humbuckers? Is there a difference? –  filzilla Oct 11 '12 at 18:03
I'm using PRS guitar having Humbucking pickups already. –  Bijoy Thangaraj Oct 12 '12 at 1:50
For the last 20 years I've assumed this is how guitars are - especially in modern houses with all kinds computers and what-not all over the place. –  Todd Wilcox Apr 10 at 12:56
@ToddWilcox You are right. When you earth your body you no longer act as an antenna for EMI so hum reduces. I covered this here:… –  Fergus May 31 at 22:10

4 Answers 4

up vote 8 down vote accepted

Your guitar is picking up mains hum. This is very common, and as you correctly surmised is due to how the components are grounded and shielded.

Usually this is simple to fix. The first items to check are:

  • your guitar lead and amp - does the noise go away if you use different ones?
  • all solder joints. Are they all solid?
  • all components are grounded, with short connections to the common ground?
  • is there a grounded shield? And if so, is everything connected to it?
  • move the selector switch - does the noise vanish in some positions? This will indicate a dodgy connection in the positions where the noise occurs.
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terminology check: by lead, you mean the cable? –  luser droog Oct 13 '12 at 4:12
Yes, the lead from guitar to amp- common source of problems as they flex and are plugged in and our. –  Dr Mayhem Oct 13 '12 at 10:33
The guitar is not picking up mains hum - The player is. When the player is earthed he/she no longer acts as an antennae and the EMI is reduced, as the OP describes. If you want to remove this noise at all times you need to earth your body by alternative means, ie an earthing wrist strap. (Or, you know, touch the strings like guitarists often do...) –  Fergus May 31 at 22:15

It does sound like a grounding issue.

The first place to check will be the jack socket on the guitar. There should be 2 wires attached to it. One that connects to the tip of the jack - this is the hot (the wire that carries the signal from the guitar) and one that connects to the outer sleeve of the jack - this is the ground.

The ground wire is usually black. Follow this wire and make sure that it is connected to the back of every tone and volume pot and the outer sleve of the switch. There should also be a wire that goes off the the bridge which grounds the bridge, strings and tuners.

If you find that all the wires are connected correctly, it could be your guitar lead that has a fault. Try a different guitar lead.

Hope this helps

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I see this is an old question, but I think I have another possible answer. I've read a lot of rubbish about fluorescent light noise, but haven't found the answer anywhere. I eventually figured it out myself. I hope this answer will help the next person who comes across the same problem!

It sounds to me like you've got either an earthing problem with your amplifier or an earthing problem with your home electrics. When mains AC passes through a transformer, the 'low voltage' side of the transformer is 'floating', and not connected to earth. This means that the '0Vdc' leg of the rectifier - which is connected to the guitar - will float at mains frequency. This doesn't matter as far as the amplifier circuits are concerned - all the rectifier voltages float together, but it does mean that the metalwork on your guitar will be floating round in potential at a harmonic of the mains frequency. This is where the hum comes from.

It a correctly designed amplifier circuit, this is easily solved: the 0Vdc in the amplifier is connected to earth. This stops the voltage floating, eliminating the hum.

If the amplifier isn't properly earthed, you yourself act as the earth connection - but only when you touch the metalwork on the guitar. That's why you get the hum when you're not in contact with the strings.

I would suggest that you start by checking your amplifier's mains plug: you should really have a three-pin plug with a separate ground pin. If that doesn't solve it, either there's an internal problem with your amplifier, or there is something wrong with the electrics in your house.

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Do you mean grounding instead of earthing which is mentioned in the other two posts? –  Dom Feb 21 at 21:04
I certainly mean earthing - in the UK, our three pin plugs have an earth terminal which should be connected to the chassis. What I certainly don't mean is connecting to the AC neutral - that could be very dangerous. –  Dan Feb 21 at 22:06

Grounding is an issue with a lot of guitars. I build and customize guitars. I've use a lot of these methods. Always check solder joints (if the solder joint is not shinny, then it's probably a cold joint). I check every connection before making the final wiring. I use a small amp (battery power) thus eliminating 60 cycle hum, to check my connections. Once you've decided what's causing the hum (amp or guitar), then you zero in of the fix.

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