The K&K Acoustic Pickups - Pure Preamp is a time-tested external preamp from one of our favorite acoustic pickup builders. +/- 20db bass, mid, and treble controls plus an internal gain trimmer gives you total control over you guitar or acoustic instrument. 10-30,000Hz frequency response can cover a huge range of acoustic instruments with the bass roll off at 100Hz, midrange at 1.5kHz with an extra large bandwidth and treble shelf at 10kHz. Input impedance is 1 meg and output is low ohmic. Battery life is about 180+ hours.