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Eliminating Troublesome Hum & Buzz Created By Electric Guitars
A wide range of solutions to this annoying, frequent problem that happens in the studio and on the stage. Plus, a discussion of power issues, including a sidebar by noted audio consultant Jim Brown.
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You’re recording an electric guitar, or amplifying it through a P.A., and there it is: hum! This annoying sound is a common occurrence.

Acoustic guitars fitted with pickups can have the same problem.

Hum is an unwanted 60 Hz tone—50 Hz outside the U.S.—plus harmonics. If the harmonics are especially strong, the hum becomes an edgy buzz.

Let’s take a look at what’s going on and how to fix it. First we need to review how an electric guitar works.

Inside The Electric Guitar
Built into the guitar, under the strings, is a magnetic pickup: a transducer that converts the strings’ vibration into an electrical signal. The pickup is a bar magnet wrapped with thousands of turns of wire, forming a coil.

When the player plucks the steel strings, they vibrate next to the magnet, producing a similar vibration in the magnet’s magnetic field, which in turn causes a varying current in the coil.

Another type of pickup uses a separate magnet under each string. Some pickups have a screw on each magnet’s polepiece to adjust the distance between the polepiece and string, allowing level control of each string.

A humbucking pickup uses two coils wired in series but with opposite polarity so that they cancel common hum fields. One coil is mounted far from the strings.

The high-impedance signal from the pickup coil goes through a simple circuit (Figure 1) and comes out the unbalanced guitar jack.

Components in the circuit are usually connected by single wires. The sleeve (ground) terminal on the jack is connected to the pickup coil, the strings, and the shield around the circuit.

Figure 1: A typical electric-guitar circuit. (click to enlarge)

From the guitar jack, the signal travels through a guitar cord: an unbalanced shielded cable.


At the end of the cable, the signal can go to several destinations: a direct box, a guitar amp, a mixer’s high-Z input, or guitar stomp boxes/processors.

Most acoustic-guitar pickups are piezoelectric types installed under the bridge or saddle. Vibrations of the guitar body flex the pickup, which generates an electrical signal. It’s very high impedance, and often is run through a preamp built into the guitar which reduces the impedance.

Whether the guitar is electric or acoustic, any component in the signal chain is susceptible to picking up hum and buzz, especially because the entire circuit is high-impedance unbalanced.

Hum Sources
Alternating current in a building’s power wiring generates electric and magnetic fields that oscillate at 60 Hz and its harmonics. Hum fields also radiate from lighting circuits and fluorescent lights.

The magnetic fields couple inductively to the guitar wiring. When the magnetic lines of force cut the conductors in the guitar and its pickup, the conductors generate a 60 Hz signal, which is amplified by the mixer or guitar amp.

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Comments (12) Most recent displayed first | All comments in chronological order
Posted by Bruce Bartlett  on  10/22/11  at  05:42 AM
Thanks for the kind words, Alton.
Posted by alton100  on  10/21/11  at  11:00 PM
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Posted by Bruce Bartlett  on  09/18/10  at  03:43 PM
See if hum-bucking guitar pickups reduce the lighting buzz you hear from the guitar amps. Maybe the amps, guitars or guitar cables are picking up RFI or EMI radiated from the lighting circuits, rather than picking up interference through the AC wiring.
Posted by Jak Florek  on  09/18/10  at  01:56 PM
Any ideas PLEASE to solve this VENUE problem: Lighting rig on it's own = no buzz. Guitar amps on their own = no buzz. Amps + lights on = horrendous buzz. BUT - p.a. power amps don't buzz. Guitar amps buzz with guitars plugged and some do even without a guitar plugged in. The building has been rewired - separate clean circuit for sound. Makes absolutely no difference which sockets we use for anything... buzzzzzzzzes. And sometimes... it disappears! Then it's back next day. Electricians have run out of ideas... seems there's no faults in wiring + no faults in Lighting Rig (new, not on same circuit as sound).
Posted by Bruce Bartlett  on  04/08/10  at  08:41 AM
If the PA system and guitar amp are grounded to different AC circuits (rather than to a common AC distribution system), then there still can be a voltage difference between the two grounds. Grounds in different locations in a venue are not always equal voltage relative to each other. You are right; before guitar amps had grounded AC plugs the shock hazard was much greater.

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