Locate the control panel on the front of the Purity preamplifier. Starting from the left, the first button is the display button, which toggles the LED volume display on the front panel. There is a small blue LED light above the switch that indicates it is on.
Find the mute button, which is directly to the right of the display button. The mute button, much like the display button, has a blue LED above, indicating its activity. If the blue LED is shining, the mute button is active, and no audio is heard.
Locate the middle of the control display. There is a large metal knob surrounded by two LED displays. This is the volume button, and the numbers displayed on the sides of the knob are the volume levels for the left and right channel, respectively.
Look at the right side of the panel. There are three buttons with the labels Source, Phase and Source. Above the buttons are numbers one through six, each with two LEDs accompanying every number. If you adjust the source buttons, the left button toggles the uppermost LED, which indicates the input source, and the right toggles the output source. Look on the back of the Purity preamp to find the corresponding inputs and outputs.
Locate the phase button in-between the two source controls. There are blue LED above and below this control, indicating which phase the Purity preamp is set to. Unless the audio is lacking in bass or has too much bass response, the phase should not need adjusting.