XLR Cable 100 ft: Thirty Metres, Still Balanced
Quick answer / TL;DR: Short answer: a 100 ft XLR run is fine for low-impedance microphones and for line-level sources. It becomes marginal when a high-impedance source drives a high-capacitance cable, which rolls off treble. Choose low-capacitance cable, keep the shield connected at one end only where a ground loop exists, and test the full run rather than a short sample.
A patch cord is a stranded assembly: moulded boot, eight contacts, T568B.One hundred feet is about thirty metres. Balanced audio still works cleanly at that distance, but capacitance and source impedance start to matter.
The deciding factor is what is driving the cable, not the length alone.
The Capacitance Question
| Source impedance | Cable capacitance | Effect at 100 ft |
|---|
| Low, under 200 ohm | 30 pF per ft | Negligible |
| Medium, 1 kohm | 30 pF per ft | Slight top-end loss |
| High, 10 kohm | 30 pF per ft | Audible roll-off |
| High, 10 kohm | 60 pF per ft | Clearly dull |
The figures are illustrative of the trend rather than measured values: capacitance forms a low-pass filter with source impedance, so both numbers matter together.
Grounding Practice
- Connect the shield at the destination end for a loop break
- Never lift both ends
- Avoid running parallel to mains for long distances
- Use star-quad construction in high-RF environments
Star-quad costs more and rejects magnetic interference better, which is why it appears in venues with dimmer racks nearby.
Real-World Applications
A pulpit mic 100 ft from the mixer is a normal install and needs nothing special. A vintage instrument with a high-impedance output over the same distance needs a DI box near the instrument, not a better cable.
Standards and Verification
| Reference | Relevance |
|---|
| AES14 | Interconnection practice |
| IEC 60268 | Sound system equipment |
| IEC 60332 | Flame propagation |
Measured frequency response for a specific combination is not provided in the knowledge base. Test the installed run end to end.
Practical Notes
Coil long cable in a figure of eight rather than a tight loop. Tight coils create an inductor and can pick up hum.
Related reading: audio cable — blogs/news/audio-cable
Related reading: 3 ft xlr cable — blogs/news/3-ft-xlr-cable
Related reading: xlr cable 50 ft — blogs/news/xlr-cable-50-ft
Frequently Asked Questions
Does 100 ft degrade audio?
Only with high-impedance sources or high-capacitance cable.
Should I lift the shield?
At one end only, and only to break a loop.
Is star-quad worth it?
In high-interference venues, yes.
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