Aguilar OBP-3SK/PP Onboard Preamp Includes stacked Treble/Bass pot and separate Mid pot. Mid pot is push/pull for Midrange frequency selection plus/minus 18dB bass at 40Hz plus/minus 16 db of cut and boost at either 400Hz or 800 Hz plus/minus 16 dB @ 6.5KHz Battery life: 324 hours