The front panel on the HP4 is divided into three sections. These are the potentiometers (knobs), headphone jacks, and buttons:
Headphone Volume
The HP4 has the potential to be very loud (it goes to 12). Please be careful when you first start passing sound through the unit. It is generally a good idea to start with the volume set at 1 and then bring the volume up.
Monitor Level
The monitor level knob corresponds to the output volume of the output on the back of the HP4. The level can be muted by pressing the Monitor Mute button.
Mono
When the Mono button is pushed in, each input will be summed together on each output. For example, if you plug a CD player into the left input and press the mono button, the signal from the left input will be present in the left and right headphone and master output. When the Mono button
