Ground Resistance and Noise
Ground loop noise voltage:
V_noise = I_ground × R_ground_path
Required ground resistance for quiet system:
R_ground < V_noise_acceptable / I_ground
Worked example:
Amplifier draws 50A average. Acceptable noise floor: 1mV (-60 dBV).
R_required = 0.001 / 50 = 0.00002Ω = 20 μΩ
This is extremely low — essentially impossible with real wire. The reason ground noise is manageable in practice is that the audio signal is much larger than the noise floor requirement at typical listening levels. The critical ratio is signal-to-noise, not absolute noise.
Practical target: Ground resistance < 0.1Ω, measured from amplifier chassis to battery negative.