Just as you wouldn’t use a massive power cable to connect your hifi up at home, so the correct choice of cable is needed to connect up a professional sound system. In order to achieve this, a knowledge of the different signal levels you’ll be using is needed.

Microphone level

This is the weakest signal you’ll encounter and is produced by microphones. It is very susceptible to interference and so should be carried by balanced cables only (see sound guide – balanced vs unbalanced). Sound desks always need to amplify this signal before they can do anything with it.

Instrument level

This is produced by most instruments such as electric guitar and bass. It is slightly greater than microphone level but it still pretty small. Balanced cables are definitely advised, especially on long cable runs.

Line level

This is a large level is most respects, being much greater than mic or instrument level. It is produced by CD players, MD players and most things than look like they should be in a hifi system (mainly because hifis primarily use line level sources). For short runs, balanced cables are unnecessary because most interference has little effect of such a large signal.

Speaker level

Compared to the other levels, this is in a different league. Unlike previous examples, the output produced by amplifiers isn’t designed to tell other electronics what to do, its to shift a big, heavy speaker cone back and forth with great power. This means that the signal is much larger and requires a thicker cable, although it isn’t usually affected by interference. Giving a mixer a speaker level source (ie. plugging the outputs of an amplifier into the inputs of a mixer) will result in damage to the mixer. At best, it’s a blown fuse; at worst, you’ve just destroyed your desk.

Cable

Signal cable

Capable of carrying mic, instrument and line level signals. They are usually terminated with XLRs, jacks or phono connectors.

Speaker cable

Much thicker and capable of carrying high currents, these are usually terminated by Speakon connectors although XLR and jacks are used in some speakers. Speaker cable can be used to carry smaller signals (eg. line level) but you’ll get a pretty poor quality signal out the other end.