“Jon, I’m in the studio and there’s this horrible, obnoxious 60 cycle buzz coming out of the guitar amp! Is the amp blown? You have to help me! What do I do?”
“Hold on, babe, it’s probably not the amp—it’s more likely the pickups.”
I sat up, almost awake. I think I tried to explain to her that every transformer in every piece of gear in the studio throws out an electromagnetic field that gets picked up at the guitar and amplified right along with the vibrations of the strings. Sometimes the hum can seem as loud as the music, which is not good. I was babbling.
“See if the guitarist is using a fuzz box, or a compressor, or if his amp is turned up to 11. Maybe the noise will go away if he turns down a little.”
Who is this, I wondered? The voice sounded familiar. Could this be a chance to help a damsel in distress?
I wanted to explain to her that even if the noise is relatively quiet compared to the sound of the guitar, it intermodulates with the picked notes and produces overtones that are not musically related—sort of like a ring modulator. The brain recognizes these subtle dissonant overtones as “yucky sound,” but I was interrupted.
“We tried that but the engineer likes this level.”
“Did you try putting the guitarist and his amp inside a 6 foot cube of grounded chicken wire?” I knew she hadn’t tried that. Hey, she woke me up!
“OK, try turning off every unused piece of equipment. Power amps, guitar amps, effects boxes and anything digital should be powered down one by one to see if that reduces the noise. Light dimmers are especially bad. Look for any neon beer signs and turn ’em all off.”
“Next, tell the engineer to look at the guitarist’s grounding scheme. Sometimes pesky hums are caused by ground loops, which can be eliminated by ground-lifting one or more pieces of inter-connected gear. It’s OK—they’ll get their ground from the audio interconnect instead of from the power cord. But always remember to leave at least one piece of gear grounded! And please forget that I was the one who told you this, next time your singer gets stung by lip-lightning.”
She had me on hold for a while, but came back with “That didn’t really help.” At this point I recognized her voice. She had recently cancelled a session at my studio. I suppose I still wanted to help her, but now I was less than enthusiastic.
“Has the guitarist walked around the room to see if his position makes a difference? Tell him to take a hike. Once he finds a relatively quiet spot, then he has to find the best orientation relative to the fields in the room. That’s right. Tell the guitarist to get a chair, sit on it and rotate.”
“Usually that’s enough to bring the hum down to a manageable level. Still not enough? See if the guitarist is using humbuckers, which are double-coil pickups. That will help a lot. Have him try all his switches and knobs to see if that makes a difference. Maybe try a different guitar. Oh, you gotta have this sound—OK...”
“Have you tried a noise gate? Various companies make them for guitar. There’s probably one in that studio rack there somewhere. Some obscure preset on a reverb box, perhaps. Oh, you have one. Why didn’t you say so?”
“Can it do downward expansion? Great, that’s even better. Expanders don’t go on and off like gates do, they ramp up and down, which is more musical. Even better is to chain two of them together—set the first one so that it doesn’t clip off the attack transients and produces only a moderate noise reduction. Use the second one to reduce the noise completely, again, leaving the attack transients.”
“That’s too complicated. Isn’t there an easier way?”
“Sure. Sample the hum, reverse its polarity and fly it into Pro Tools, line it up with the real hum and use it to cancel the hum on the track.” I paused a moment for that to sink in.
“And honey, if that doesn’t work, take two aspirin and call me in the morning.”
Jon Bare is the author of Recording The Electric Guitar—It’s All About Tone, in the Playback Platinum series.