Speaker cables and instrument cables often have the same plugs on the end, which makes them easy to mix up. They are built for different jobs, and using one for the other can cause noise, lost tone or, in the worst case, damage to your amp.
What each cable does
An instrument cable carries a weak, high-impedance signal from a guitar or bass to a pedal or amp. It has a thin central conductor surrounded by a shield that keeps interference out.
A speaker cable carries the amplified output of a power amplifier to a speaker. That signal is strong, low impedance and carries much more current. A speaker cable has two heavier conductors of the same size and usually no shield, because the signal is strong enough that picked-up noise is not an issue.
How to tell them apart
| Instrument cable | Speaker cable | |
|---|---|---|
| Conductors | One thin center wire plus a shield | Two heavier wires of equal size |
| Shield | Yes | Usually none |
| Thickness | Thinner | Thicker for the same length |
| Plugs | 1/4 inch TS | 1/4 inch TS, Speakon or banana plugs |
| Marking | Often says instrument or guitar cable | Often says speaker cable and may list the gauge |
Why an instrument cable is the wrong choice for a speaker
The thin center conductor adds resistance and cannot handle the current a power amp produces. At best you lose output power. At worst the conductor heats up and the cable can fail, which can leave the amplifier with an open or shorted output. That is a particular risk with tube amplifiers, which need a speaker load connected to run safely. Never use an instrument cable to connect an amp head to a speaker cabinet.
Why a speaker cable is the wrong choice for a guitar
A speaker cable is unshielded, so it picks up hum, and the two closely spaced conductors add capacitance that rolls off treble. It may seem to work, but the guitar will sound duller and noisier. See how cable length affects tone.
Choosing the right speaker cable
The main choice is thickness, measured as gauge, and the right one depends on cable length and speaker impedance. See the speaker cable gauge guide for a chart.
Label them
If you own both kinds, label them. Colored tape or heat-shrink at each end makes it obvious which is which, and it avoids the mix-up in a dark venue or a rush at the end of a gig.