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Q. Can you help me reduce studio hum?

I have a problem with a new studio installation that I'm just getting to the point of completing. This is the third time over the past 12 years that I have relocated my studio (each time adding a bit more kit) and I have never had a problem with audio noise/hum like the one I have at the moment.

Knowing that ground loops can be a potential problem, I have the studio equipment powered from a distribution board, with all the grounds centred in one junction box. As far as possible, the audio leads are located away from the mains power leads. I've tried unplugging everything and carefully plugging in one lead at a time, checking for hums as I go, but this falls flat quite quickly, as nearly every bit of equipment, once plugged into the desk (which is nice and clean with nothing plugged into it!) creates a hum at around 50Hz. Strangely, two bits of equipment (the Korg DW6000 synth and an old digital delay unit) are perfect. They emit a bit of hiss, as you'd expect, but absolutely no hum. Everything else has hum.

Just to make things more odd, most of this equipment worked 100 percent hum‑free in my last studio space. The only thing that has really changed is the location, and the power socket the power distribution board plugs into. The new studio space is in an industrial unit, near a main road. Any possiblity that there may be external interference getting into the cables?


Editor Paul White replies: It can be hard to pin down hum problems without actually being in the studio in question, but I think you may have a poor system earth, in which case getting a new earth spike banged into the ground and connected to your mains earth wiring might help. I've also found that connecting unbalanced equipment using pseudo‑balanced leads helps a lot. I don't know if you've tried this permulation, but essentially you wire a balanced jack lead conventionally at the mixer end, then at the other end fit a mono jack wired hot to tip, cold to the bit where the screen usually goes, leaving the screen from the cable disconnected.

I feel that the cause is unlikely to be interference, as the problem is hum rather than buzz, though apparently weird things can happen on industrial estates, due to unbalanced current draw from the original three‑phase mains supply by companies using high‑power equipment.

Take care with the audio connections between your mixer and monitor amp and try ground lifts if the connection is balanced.