A preamp is for "amplifying and adjusting the sound beforehand. For acoustic guitars and electric accos, the sound picks up is small, so if you amplify it with the amplifier, you will receive a lot of noise. In particular, when playing acoustic guitars on the stage, it is necessary to adjust and amplify the volume with the noise suppressed arpeggio, and the strong attack cord playback. Preamp may not be able to understand what you need, but unlike an effect that changes the tone of the tone, but when it comes to acoustic guitars and bass, preamplifiers are essential for you. When you pick up the acoustic guitar sound with a microphone, amplifying with the preamp is required and there is often a minimum adjustment possible with the preamp installed on the body of the electric acoustic guitar, and it is often insufficient. INPUT CLIP Indicator: When this indicator is lit, the input level is too large, so it may cause sound cracks. Adjust level with INPUT knob. Treble BOOST Switch, you can lift treble that tends to weaken due to the output of an acoustic guitar. The ANTI FEEDBACK switch allows you to manually inspect the frequency that occurs in a range of 80 Hz to 300 Hz. Can be directly connected to the BALANCED OUTPUT XLR output terminal, mixers, sound cards, and other acoustic equipment XLR input terminals. Works with 9V center negative adapter and 9V batteries. Weight: Approx. 28.7 oz (800 g); Size: L 5.5 x W 5.7 x H 2.2 inches (140 x 145 x 5