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Q. Can I reduce equipment noise?

By Paul White
Published June 2001

I am having problems controlling all the noise generated by the equipment on my desk. I have two Roland VS1680 multitrackers, both with CD‑ROM drives, a Behringer headphone amp, a Mackie 1604 mixer, and an external hard drive, all on the same desk. All of this generates hum and other noises, which are amplified by my Quad Amp, driving a pair of Spirit Absolute 2 Monitors, as well as a pair of big Mission hi‑fi speakers. Although it seems to be mainly from the CD drives, I can't seem to stop all of the noise. If it is creeping into the Quad amp through the cables, which ones? The inputs to the preamp, or the cable between the preamp and the power amp?

William Walker

Editor Paul White replies: While some of your equipment will produce physical noise (sound), there's really no reason why the audio part of your system shouldn't be quiet, providing you are using reasonable quality cable and balanced connections wherever possible. It's more likely that hum is being caused by ground loops, and though these aren't always easy to remedy, here are a few things to try.

You can only take full advantage of balanced interconnects when the equipment at both ends is balanced, of course, but where an unbalanced source feeds a balanced destination, it's worth making a special cable with a conventionally wired balanced connector at the balanced end but with an unbalanced connection at the other end which leaves the cable screen disconnected. Instead, connect the cold wire (often blue) to the pin or solder tag where the screen usually goes.

Finally, when connecting unbalanced equipment together, you can try connecting the cable screen to the connector via a small 220 Ohm resistor rather than connecting it directly, as this can help disperse circulating ground currents.

Once the cabling has been sorted out, ensure that audio cables and mains cables don't run together, and also try plugging any computer peripherals or CD recorders into a separate mains outlet.