Cable Length Calculator — Maximum Audio Cable Runs

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.

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.

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.

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.

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.