RCA Level Converter

About This Tool

This tool estimates passive attenuation for RCA audio interfaces by scaling a higher amplitude signal to a lower, line level suitable for inputs or ADCs. It targets electronics hobbyists, audio technicians, and repair engineers who interface legacy RCA equipment with modern gear. The model supports common passive attenuation strategies using a voltage divider and accounts for practical input impedance constraints.
The core calculation derives an attenuation ratio a = Vout/Vin and selects resistor values that realize the ratio while keeping Rin within a usable range. In a simple divider with Vin, R1 to Vout, and R2 to ground, R2 = a/(1 − a) × R1 when the load is large; the tool also shows how to adjust for a given load (Rin) by using parallel combinations R2 || ZL and R1 || ZL. Example: Vin = 5 V, Vout = 1 V, Rin = 10 kΩ yields R1 ≈ 10 kΩ and R2 ≈ 2.5 kΩ.
Outputs include the attenuation ratio, proposed resistor values, and recommended input impedance. It does not model frequency response, PCB layout, or active buffering. It is intended as a design aid for DC/low-frequency signal interfacing and is applicable when a passive attenuator is acceptable.
Typical use cases include attenuating line-level audio from device outputs to mic or line inputs, interfacing with ADCs that require lower amplitude, and quick prototyping in audio DIY projects. The tool emphasizes simplicity, practicality, and impedance-aware guidance as a differentiator from generic calculators.

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