Difference Between Instrument Cable & Speaker Cable

Both instrument and speaker cables feature ¼-inch plugs on both ends and a single, insulated cable. Their internal construction, however, is very different. Instrument cables feature a single electrical conductor, typically 22 AWG stranded copper, which carries the guitar's signal, and an electrical shield, or ground, which surround the signal conductor in a braided fashion. Speaker cables feature two identical copper conductors running in parallel. Each is insulated, and typically a heavier 18 AWG stranded copper.

Instrument cables connect the signal conductor of the wire to the tip of a ¼-inch plug, and the electrical shield to the sleeve of the same plug. Both connectors are wired identically. This provides a clean path for the instrument's signal to the amplifier, while the shield protects the instrument's signal from unwanted electromagnetic noise or radio frequency interference. Speaker cables connect its positive conductor to the tip of the ¼-inch plug, and the negative conductor to the sleeve of the same plug.

Both cables carry different signal types. Instrument cables are responsible for transmitting the high impedance, low amplitude signal from a guitar or bass to the amplifier. Shielding is as important because this signal will become louder as the amplifier increases the signal's volume. Any unwanted noise picked up by this cable would be amplified along side of the intended instrument's signal, destroying the guitar's sound. Instrument cable's smaller gauge wire is also rated only for low voltage signals, and cannot properly handle the voltage and current of a guitar amplifier's output, making them inappropriate substitutes for speaker cables.

Speaker cables do not require shielding because the signal will not be amplified further. The main purpose of speaker cables is to provide a stout electrical path for high voltage, high current audio signals from the amplifier's output stage directly to the speaker themselves. Higher gauge wire is required to properly handle these signals, making speaker cables less physically flexible than instrument cables and typically much shorter in length.