The word amp cable gets used for three different cables around an amplifier: the shielded wire from your guitar to the input, the heavy unshielded wire to the speaker cabinet, and the power cord to the wall. Each carries a very different signal, and mixing them up is the most common amplifier wiring mistake.
Amp Cable: Matching the Right Cable to Each Amplifier Connection
Quick Answer / Summary: An amp cable is the cable that connects an amplifier to the rest of the signal chain. The right type depends on the run: a shielded instrument cable from guitar to amp input, an unshielded speaker cable from amp to cabinet, and a separate power cord for AC mains.
The Three Cables Around an Amplifier
An amplifier has three distinct cable jobs. The input side takes a small, high-impedance instrument signal through a shielded cable. The output side drives a low-impedance speaker load through a heavy, unshielded cable. And the AC side feeds the amp from the wall through a power cord.
Input, output and power
The input cable is a shielded unbalanced cable, usually with 1/4-inch TS connectors, built to protect a tiny signal from hum. The output cable is unshielded two-conductor speaker cable, sized to carry high current without resistance. The power cord is a three-conductor mains cable rated for the amp’s current draw.
Because all three can look similar at a glance, especially the 1/4-inch cables, labeling them or buying them in different colors prevents the classic mix-up of running an instrument cable to a speaker cabinet.
The Instrument Cable to the Amp Input
Between the guitar, bass or pedal board and the amplifier input, use a shielded instrument cable. The signal here is tiny, often a few hundred millivolts, so the shield is what keeps radio and electrical noise from reaching the preamp.
The shielded run to the preamp
Keep this run as short as practical, ten to twenty feet on stage, because the cable’s capacitance rolls off treble as it lengthens. A low-capacitance cable preserves the sparkle on longer runs, especially with passive pickups.
The connector is 1/4-inch TS on almost every amplifier. Match it to the jack, and prefer a plug with solid strain relief, since this is the cable that gets flexed and stepped on most.
The Speaker Cable to the Cabinet
Between the amplifier output and a passive speaker cabinet, use an unshielded speaker cable with two equal, heavier-gauge conductors. It carries high current at low impedance, so it must be thick enough to avoid resistance and heat.
Never use a shielded instrument cable here: its thin center conductor cannot handle the current and can overheat or damage the amplifier. The reverse, a speaker cable on the input, passes signal but hums because it has no shield.
For most amp-to-cabinet runs of a few feet, 16 gauge is enough, but 14 or 12 gauge is safer for long runs, bass-heavy signals and low-impedance cabinets. Speakon connectors are the modern locking alternative to 1/4-inch TS on the output side.
The Power Cord and Safety
The AC power cord is separate from the signal path and must be rated for the amplifier’s current draw. Use the cord that came with the amp or a matching three-prong replacement, and never bypass the ground pin, which protects against shock.
Keep the power cord away from the instrument cable. Running them together for long stretches induces hum into the unbalanced input, so cross them at right angles and keep a few inches of separation wherever possible.
Inspect all three cables before a session. A cracked power cord, a loose speaker connector or a kinked instrument cable is a cheap fix now and an expensive failure on stage.
The Three Amp Cables at a Glance
| Connection | Cable Type | Shielded? | Connector |
|---|---|---|---|
| Guitar to amp input | Instrument cable | Yes | 1/4-inch TS |
| Amp to speaker cabinet | Speaker cable | No | TS or Speakon |
| Amp to wall outlet | Power cord | N/A | 3-prong IEC/mains |
| Pedal to pedal | Patch cable | Yes | 1/4-inch TS |
Real-World Application Scenarios
A guitarist labels a shielded instrument cable for the amp input, a heavy 12-gauge speaker cable for the cabinet, and keeps the power cord routed away from the signal cables; a bassist uses Speakon on the output side for a locking, high-current connection; a studio checks all three cables before recording to avoid hum and dropouts.
Recommended Internal Resources
- how XLR and TRS cancel noise on long runs
- the TS connector and gauge for the speaker run
- matching AWG to run length and power
For the shielded signal path see balanced audio cable, and for the output side see 1/4 inch speaker cable.
Frequently Asked Questions
What cable do I use for an amp?
A shielded instrument cable from guitar to the amp input, an unshielded speaker cable from the amp to the cabinet, and a rated power cord to the wall. The three are not interchangeable.
Is an amp cable the same as an instrument cable?
An instrument cable is the shielded cable that feeds the amp input, so it is one type of amp cable. The term amp cable can also refer to the speaker cable on the output.
Can I use a guitar cable as a speaker cable?
No. A guitar cable is shielded with a thin center conductor and cannot handle the amplifier’s output current; it can overheat and damage the amp. Use a proper speaker cable.
Why does my amp cable hum?
Hum usually comes from an unshielded cable on the input or from running the signal cable alongside the power cord. Use a shielded instrument cable and separate it from AC wiring.