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Audio Input Loading and Cable Resistance

Estimate resistive analog input loading from source and input resistance plus a two-conductor cable loop, without a false impedance-match score.

Use this result well

Inputs that matter
Source output resistance (Ω), Receiving input resistance (Ω), Cable one-way length (m), Resistance per conductor (Ω/m)
Output to expect
Voltage delivered to the input
  • Check the units and required inputs before comparing results.
  • Keep the assumptions with a copied result so you can reproduce the calculation later.
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Reference & details

How it works

Resistive audio source-to-input loading

Cable loop resistance = 2 × length × resistance per conductor per meter; Vload/Vopen = Rload/(Rsource + Rloop + Rload) A lumped resistive voltage divider. Analog microphone and line inputs commonly bridge a lower source impedance with a higher input impedance. Cable capacitance, inductance, frequency-dependent impedance, phantom power and common-mode rejection are not modeled. This is not a transmission-line reflection, AES3/digital cable, noise-rejection or connector-compatibility calculation.

Updated: September 2026

Example Scenarios

Model a low-frequency resistive source, input and two-conductor cable loop. Compare voltage loading without treating analog audio as impedance matching.

Common Mistakes to Avoid

Applying resistive audio source-to-input loading outside its stated assumptions

Analog microphone and line inputs commonly bridge a lower source impedance with a higher input impedance. Cable capacitance, inductance, frequency-dependent impedance, phantom power and common-mode rejection are not modeled. This is not a transmission-line reflection, AES3/digital cable, noise-rejection or connector-compatibility calculation.

FAQ

Not as a general analog audio rule. Follow the device specifications; a high input impedance often reduces loading.

Yes, through the entered conductor resistance. High-frequency cable effects require a different model.

About Audio Input Loading and Cable Resistance

Estimate resistive analog input loading from source and input resistance plus a two-conductor cable loop, without a false impedance-match score. Choose the mode that matches your measurements or study design, enter the stated units and keep the method and limits with the result.