Check the listing for details. SMD DD1 Steve Meade Distortion Detector DD-1 Car Audio Amp Signal + Test Tone CD. Condition: Open box. Listed at 174.99 USD. The SMD Distortion DetectorThe purpose of this tool is to enable the installer to set the gain of an audio amplifier to match the source unit’s output level, accurately and quickly. It can also be useful for detecting distortion in the audio signal caused by poorly designed or malfunctioning audio equipment.What's in the Box?The Distortion Detector (DD-1))Protective silicon rubber bootCalibrated Test tone CDHarnessPride of ownershipThe DesignWhen you pick up the DD-1, know that you are holding a precision piece of equipment. If treated as such it should provide you with many years of reliable service. 9V batteries are the power source for a few reasons:They are readily availableIsolating the DD1-1 from the vehicle’s electrical system for power, guarantees that it will only measure what it is supposed to measure; the audio signal, not noise in the charging system.An RCA input connector is used for a few reasons:It makes it pretty easy to measure the output of a headunit directly, if you choose to do soShould the harness become damaged it is easily replaceable or repairable in the fieldSpecificationsThe Distortion Detector’s circuitry is 100% analogDistortion Detection trigger level > 1.0% Harmonic DistortionGuaranteed operating range of input signal is 1.2Vrms – 125Vrms. (15,000 Watts at 1 ohm) AutorangingSignal Present LED trigger voltage 750mVrmsLow Battery LED trigger battery voltage < 5.6VdcAuto-shut off timer 8 - 10 minutes after ON button is pressed