Combining a pristine bass preamp with a studio-quality Direct Out in a Phase 90 sized box, the MXR Bass Preamp features separate input and output controls and a 3 band EQ section with sweepable mids - from 250 Hz to 1 kHz. It’s all delivered super clean with high headroom thanks to Constant Headroom Technology™; use the pre/post EQ switch to set whether or not the Direct Out signal is affected by the EQ section. The ground lift switch removes ground loop hum. Switchable buffered Direct Out or true hardwire bypass. Powered by 9 volt battery or AC adaptor (ECB003).