Turn off the 737 if it is on. Connect your instrument or microphone to the correct input jack. Connect a passive microphone to the balanced XLR input on the back of the unit. Other microphones and instruments can be connected to the XLR jacks on the back or the input jack on the front.
Turn the “Input” knob to “Line” for powered instruments, or to “MIC” for microphones that require power. Press the “High Gain” button if using a passive microphone.
Turn the equalizer knobs and all other knobs to neutral. Equalizer knobs that are set low can lower the overall volume.
Turn down the “Preamp Gain” knob, then turn on the unit. Test your instrument or microphone while you slowly turn up the “Preamp Gain” knob. Continue turning the gain up until the input level is acceptable.