K&K Pure Preamp, featuring +/-20 db bass, mid, and treble controls plus an internal gain trimmer, this belt clip unit has been specifically designed for the frequencies of the acoustic guitar but it is also great for many other instruments, features a special super wide band midrange filter, which is absolutely great in combination with the Pure pickups, frequency response is 10-30,000Hz, the bass control is set to roll of at 100Hz, the midrange at 1.5kHz with extra large bandwidth and the treble are set at 10kHz, input impedance is 1 meg and the output is low ohmic, battery life is about 180+ hours.