Technical How-To
How to Test Audio Cables with a Multimeter
Before throwing out a cable that works only when you hold it just right, reach for a multimeter. In a few minutes you can discover broken conductors, shorts, swapped pins and intermittent connections. Here’s how to test the common studio cable types and how to interpret what the meter tells you.
Set up safely
Disconnect the cable from all equipment. Set the meter to continuity or low resistance and first touch its probes together to learn the meter’s normal lead resistance and audible response. Never perform resistance or continuity tests on energized circuits.
Balanced XLR cable
On a conventional XLR cable, probe pin 1 to pin 1, pin 2 to pin 2, and pin 3 to pin 3. Each should show a low, stable resistance. Then test the different pin pairs at each end: 1–2, 1–3, and 2–3 should be open on a normal straight-through cable. Wiggle the cable gently at the connectors during each continuity test.
| Probe at end A | Probe at end B | Expected |
|---|---|---|
| Pin 1 | Pin 1 | Continuity |
| Pin 2 | Pin 2 | Continuity |
| Pin 3 | Pin 3 | Continuity |
| Pin 1 | Pin 2 or 3 | Open circuit |
| Pin 2 | Pin 3 | Open circuit |
TRS cables
For a straight-through balanced 1/4-inch TRS cable, tip connects to tip, ring to ring, and sleeve to sleeve. Check all three paths independently, then verify that tip, ring, and sleeve are not shorted together. Distinguish a TRS balanced cable from a stereo headphone lead: the conductor assignments may be physically identical, but equipment expectations differ.
TS and instrument cables
For a typical mono TS cable, tip should connect to tip and sleeve to sleeve, with no tip-to-sleeve short. Coaxial instrument cables may show very high resistance from tip to sleeve; that is normal. A speaker cable requires the correct conductor gauge and connector type and must not be mistaken for an instrument cable.
Intermittent faults and polarity
A beep at rest does not prove a cable is sound. Flex the last few inches near each connector while watching resistance. For unfamiliar or custom adapters, draw the intended wiring diagram before measuring. A cable can have full continuity but still reverse polarity because its conductors are cross-connected.
When a multimeter is not enough
Continuity tests cannot reliably reveal excessive capacitance, poor high-frequency shielding, insulation defects under operating voltage, or all faults that emerge under vibration. For digital audio, RF, or long installed runs, use an appropriate cable tester and specifications.
Safety: Never use the ohmmeter on an outlet, powered amplifier output, or cable connected to live equipment.
