Balanced vs. Unbalanced Cables
Q I have a legacy AV receiver (Integra DTR-7) and am considering replacing it with a separate preamp/processor and amplifier. I’ve noticed that some preamps only have RCA outputs, while other, more expensive preamps also have balanced XLR outputs. Is there a noticeable difference in the sound quality when using balanced XLR cables versus unbalanced cables? The length of the cables needed to connect the two units would only be 1 meter. —Ed Mendelson / via e-mail
A The main reason you’d want to use balanced cables in an audio system is to prevent noise from being induced over long cable runs. With a balanced connection, the signal is conveyed from the source along two separate wires, with a third serving as a shield. (The signal is in phase on the first wire and phase-inverted on the second.) Any electromagnetic interference that the cable detects appears equally on each wire, and when the amplifier at the other end subtracts the two lines, it effectively cancels out the noise. In an unbalanced RCA-jack connection, there are only two wires—one to convey the signal, and a second to serve as a shield (and ground). The shield wire protects reasonably well against external noise, but some noise can still reach the audio signal, which could have audible effects. Having said all that, 1 meter is a short run—it’s highly unlikely that you’ll experience any noise issues. For that reason alone, I’d recommend saving money and going the unbalanced route for your new preamp/amp purchase.