How long can a balanced XLR cable be?

A balanced XLR microphone cable can typically run up to 100 metres without significant signal degradation. The balanced connection rejects interference (common-mode rejection), and the low source impedance of a microphone or preamp keeps the cable’s capacitive high-frequency roll-off far above the audio band, so long runs stay flat. Balanced line-level cables can run even further due to higher signal voltage.

Why should instrument cables be kept short?

Instrument cables are unbalanced and carry a high-impedance signal from passive pickups (around 10 kΩ). The cable capacitance (typically about 100 pF per metre) forms a low-pass filter with that source impedance, so longer cables audibly roll off treble. Tone loss becomes noticeable beyond roughly 6 metres (20 ft); 3–4.5 metres is ideal. Use a DI box or active buffer for longer runs.

How is the high-frequency roll-off worked out?

For analogue cables the dominant loss is capacitive. Total capacitance is the per-metre figure multiplied by length, and it forms a low-pass filter with the driving source impedance: the −3 dB corner frequency is f = 1 / (2π × R_source × C_total). A low-impedance balanced source pushes that corner well above 20 kHz; a high-impedance passive pickup brings it down into the audible range as the cable gets longer.

How much signal does a speaker cable lose?

Speaker cable loss is resistive, not capacitive. The cable resistance forms a voltage divider with the speaker impedance, so loss in dB = 20 × log₁₀(1 + R_cable / Z_load). Aim to keep this under 0.5 dB. 16 AWG into an 8 Ω speaker reaches about 15 metres at that limit; heavier 14 or 12 AWG cable runs further and also preserves damping factor.

Why are digital cables limited by length too?

Digital links (AES3/EBU at 110 Ω, S/PDIF at 75 Ω) don’t fade gracefully like analogue — they fail by jitter and eye-closure once the cable degrades the signal edges too much. AES3 per EBU Tech 3250 is specified to 100 metres; S/PDIF coax is practically limited to around 10 metres.

AudioCalcs

Cable Length Calculator — Maximum Audio Cable Runs

Calculate maximum cable length before signal degradation for different cable types.

Cable TypeSelect your cable type or enter custom specs

Cable Length

Total cable run length in metres

How We Calculate This

Maximum cable lengths are set by the signal type and the way each cable class loses signal. There is no single flat “dB per metre” figure — each class fails by a different mechanism.

Analogue (capacitive): f(−3 dB) = 1 / (2π × R_source × C_total), where C_total = capacitance (pF/m) × length. High-impedance unbalanced sources roll off treble; low-impedance balanced sources stay flat.

Speaker (resistive): loss = 20 × log₁₀(1 + R_cable / Z_load) — keep under 0.5 dB.

Digital: jitter / eye-closure limited; AES3 to 100 m, S/PDIF coax to ~10 m.

Balanced connections carry the signal on two conductors with opposite polarity. Any interference picked up affects both equally and is cancelled at the receiving end (common-mode rejection), allowing much longer runs than unbalanced connections.

Frequently Asked Questions

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Last updated: June 2026

All calculations are estimates based on standard formulas. Always verify results for critical applications.