Audio Attenuator
L-pad design
Enter source/load impedance and the attenuation; RL and RT appear live.
Component values
How to use this calculator
An L-pad is two resistors that reduce a signal by a set amount while (ideally) preserving the source impedance seen by the load. For a target attenuation, the voltage ratio is K = 10^(−dB/20), and the series and shunt resistors are RL = Zs·(1+K)/(1−K) and RT = Zs·(1−K)/(1+K). Enter the system impedance, the load, and the dB, and the two resistor values appear live.
What it means in a real circuit
Attenuators let you trim a level to match another stage without changing the system's characteristic impedance — classic in balanced 600 Ω audio lines and in protecting sensitive inputs from overdriving. Use this to build a fixed pad, or to figure out how much gain you've lost when a pad is inserted. For large attenuations the shunt resistor gets small, so choose a power rating with margin.