Managing Cables with Different Audio Levels

Audio systems incorporate signals with a wide range of levels and care needs to be taken in cable management.

Microphone level signals can range from -80 dBu to around -20 dBu (referenced to 0.775 volts), with nominal levels around -60 dBu to -50 dBu.

Analog line level signals range from -20 dBu to +30 dBu, with a common operating level at +4 dBu.

For high-level signals, as used for loudspeakers, the levels start at around +30 dBm (referenced to 1 mW) and go up from there.

Digital audio voltages can be either 4 volts nominal for AES3 balanced or 1 volt peak-to-peak for AES3id unbalanced.

On top of that, audio systems usually employ control signals of various sorts.

It's good engineering practice to keep each category of cable grouped by itself and away from other groups of cables with different levels. Run each group in separate conduits or cable raceways. Especially keep very low-level signals like microphone circuits away from very high-level loudspeaker cables.

Such care in audio cable management helps prevent instability in the system. Microphone level wiring is especially susceptible to crosstalk from adjacent high-level signals as well as control. Because of the high-gain of microphone level circuits, oscillations could start and even become self-sustaining depending on the crosstalked signal.