At its heart, the Double Back is a low noise, low distortion compressor-sustainer pedal with very wide-range compression, exceptional sustain, and simple, intuitive control of compressor dynamics. One control knob adjusts the compression ratio from 1:1 to over 20:1, and simultaneously sets the maximum sustain, with an extraordinary 50dB of sustain gain being engaged at high compression ratios. Added to this are three features that preserve the playing dynamics and "feel" that are lost with many other compressors. The first is the "Double Back" control. The second is a three-position switchable "Frequency Filter" that allows the tone of this sound to be tailored to fit the music and the player's taste. The third is the "Attack" control which determines how fast the compressor responds to each pick attack. The range of this control is enormous. At its fastest speed, the compressor action is almost instantaneous - the guitar sound is compressed as soon as the pick releases the string. At medium speeds, the initial organic "thunk" of the guitar body gets through before the compressor acts. At the slowest speed, a massive explosion of sound precedes the sustained tone, hammering out the guitar dynamics while still providing incredible sustain.

The SFX-09 is the cleanest, quietest compressor around. And with the Double Back feature, it's one of the most unique and usable.