Audio Cable: Signal Level Decides the Cable
Quick answer / TL;DR: Short answer: use balanced cable (XLR or TRS) for long runs and low-level signals, unbalanced coax for short line-level links, 75 ohm coax for digital S/PDIF, and proper speaker cable for amplifier outputs. Never connect speaker level to a line input. Keep unbalanced runs short and away from mains.
Four audio lines: balanced XLR, TRS, unbalanced RCA, and speaker cable.Audio cables differ by signal level and by whether the link is balanced. Those two facts determine shielding, impedance and usable length.
Choosing by connector shape alone produces hum, noise and damaged inputs.
Signals and Cables
| Signal | Level | Cable |
|---|
| Microphone | Millivolts | Balanced XLR |
| Line | About 1 V | Unbalanced RCA or balanced TRS |
| Digital S/PDIF | Two-level | 75 ohm coax or optical |
| Speaker | Tens of volts | Speaker cable |
| Phono | Millivolts | Screened, short |
The phono row is the one that catches people: a turntable needs a preamp nearby, not a long cable.
Practical Rules
- Balanced for long runs
- Unbalanced short and away from mains
- 75 ohm for digital coax
- Speaker cable for speaker outputs
- Never mix levels
Mixing levels is destructive, not merely loud: a few watts into a line input destroys it.
Real-World Applications
A stage mic 20 m from the mixer uses balanced XLR. A subwoofer 3 m from a receiver uses an unbalanced RCA lead. A television feeding an amplifier uses optical or coax digital.
Standards and Verification
| Reference | Relevance |
|---|
| IEC 60958 | Digital audio interface |
| IEC 60268 | Sound system equipment |
| AES14 | Professional interconnection |
Input types for specific equipment are not provided in the knowledge base. Check the manual before connecting.
References
- IEC 60958, Digital audio interface
- IEC 60268 series, Sound system equipment
- AES14, Professional audio interconnection
Practical Notes
Label cables by signal type at both ends. Unlabelled cables get plugged into the wrong level eventually.
Related reading: audio cable — blogs/news/audio-cable
Related reading: toslink audio cable — blogs/news/toslink-audio-cable
Related reading: rca audio cable — blogs/news/rca-audio-cable
Frequently Asked Questions
Balanced or unbalanced?
Balanced for long runs and low-level signals.
Can I use RCA for digital?
Yes, if it is 75 ohm coax.
How long can unbalanced run?
A few metres to tens of metres, depending on level.
Can speaker level go into RCA?
No. It will damage the input.
Sourcing cables for a project, a store, or a private-label line? Contact our B2B sales team for specifications, certification evidence, and volume terms – FOB and CIF options available. Request a quote or sample.
