The Main Volume control lets you adjust the Sampler volume across all slots, from off to full. You can control + click the knob to reset it to full volume.
The Mute button next to the main Volume control lets you mute the entire Sampler output, to silence all sample player slots as one group. The Mute control toggles On/Off each time you click it. You can also control + click the Mute button to momentarily change its state - this means that the audio will only be muted (or un-muted if it was already muted) for as long as you hold your mouse click or MIDI mapped button.
Use the Output selector buttons to choose where you wish to have the Sampler output audio to.
1 outputs through Channel 1
2 outputs through Channel 2
3 outputs through Channel 3 (if available on your Serato DJ hardware)
4 outputs through Channel 4 (if available on your Serato DJ hardware)
M outputs directly to the Mix (Master) output of your Serato DJ hardware
Note: Some devices show a 'A' for AUX, or their 'M' actually refers to MULTI. In the case of the former, the Sampler will be output via the auxiliary channel on that specific hardware, and in the case of the latter, will be output via summing of all available channels, ie, each channel will output 25% in the case of a 4-channel device.