The Knockout Attack Equalizer from Electro-Harmonix is a two-filter combination equalizer. The Knockout EQ is designed to work with any instrument level signal from any instrument or voice. It consists of one Low-Pass filter, one High-Pass filter, and a direct Dry signal, each with its own knob. The Low and High knobs deal with gain while the Dry signal serves as mediator between the two. The Low, High, and Dry elements may be used independently or in any combination to yield a specific and focused tonal sculpture.

The Low knob is a volume control for the low or bass frequencies; it controls the output volume from the Knockout's seven-pole Low-Pass filter and is also responsible for contouring the bottom end in relation to the total sound. The High knob is a volume control for the high or treble frequencies; it controls the output volume from the Knockout's six-pole High-Pass filter and is also responsible for contouring the high end to the total sound. The Dry knob is a volume control for the signal present at the input jack. Use the Dry knob in conjunction with the Low and High knobs to create your tone. A 9 VDC battery is included with the EQ.