1,3: Input 1, Input 2. The signal output from your acoustic instrument, tape player, rhythm machine, high-Z microphone or other source may be connected to either or both of these jacks by means of a shielded signal cable. Each of the input jacks is governed by its corresponding gain control (#2 for Input 1, #4 for Input 2). The signals from these two jacks are summed together after their input gain stages. 2,4: Gain 1, Gain 2. Use these controls to set the input gain level for the corresponding input jack. These controls set the level of the input signal and serve as the amplifier�s volume controls. 5: Low. This serves as the bass control for both channels. Adjust this control to get the best sounding bass response for your instrument. Excessive boost of the low control can cause an unnatural howling (acoustic feedback from your instrument) and should be avoided. 6: Mid. This serves as the midrange control for both channels. Adjust this control to get the best projection and midrange tones for your instrument. 7: High. This serves as the treble control for both channels. Adjust this control so your high notes and harmonic overtones are lively but not overpowering. 8: Reverb Level: Use this control to adjust the amount of reverberation added to the signal. In the fully counter clockwise position, the signal is dry (no reverb added). As you rotate the control clockwise the amount of reverb increases.