Balanced vs Unbalanced Calculator — Noise Rejection & Max Cable Length

Balanced Noise Rejection

Balanced cables reject common-mode noise (picked up equally by both conductors) by phase cancellation. The receiving device inverts one signal and adds them, doubling the wanted signal while cancelling the noise.

Maximum Length Guidelines

Unbalanced: 3-8 metres depending on environment

Balanced: 30-60+ metres depending on environment

These are practical guidelines. Actual performance depends on cable quality, shielding, and the specific noise sources present.

Cable Capacitance & HF Roll-off

Cable capacitance (typically 80–150 pF/m) forms a low-pass filter with the source output impedance. Longer cables and higher capacitance reduce high-frequency response. The roll-off frequency is estimated using f = 1 / (2π × R × C), where R is the source impedance and C is the total cable capacitance.

The result is highly dependent on source impedance. Low-impedance line outputs (≈50–150 Ω, the default 600 Ω being a conservative worst case for older gear) put the cutoff far above 20 kHz, so HF roll-off is informational only for line-level sources. It only becomes audible with high-impedance instrument sources such as a passive guitar or synth (≈10 kΩ–50 kΩ), where even a few nanofarads of cable noticeably dull the top end.