SMD Distortion Detector DD-1 PLUS - Set Amplifier gains like a PRO! The distortion detection circuitry is 100% analog, digital microprocessing system used for display and calculation of overlap Distortion Detection trigger level &gt; 1.0% Harmonic Distortion 3 stage autoranging for wide range of input signal from 1Vrms  200Vrms. (40,000 Watts at 1 ohm) Auto-shut off timer 8 - 10 minutes after ON button is pressed Battery self-test and display of condition when DD-1+ is initialized