The Electro-Harmonix White Finger Guitar Pedal yields transparent, long sustain that preserves attack. Two optocouplers (LED and lamp) offer distinctly different readings and uniquely varied compressions. The White Finger Pedal features multiple FETs instead of vacuum tubes, making it the affordable alternative.LED optocoupler for a faster attack compression Lamp optocoupler for softer blooming compressor Quiet long sustains with transparent tones Pre-gain control lets you control how hard your instrument hits the compressor Sensitivity knob for control of how the compression will be hit Compression amount allows you to dial in the perfect ratio for your music Same compression theory as our professional NY-2A but uses FETs instead of tubes 40DC-100 power supply included