ART Pro Audio USBDualTubePre - Two Channel USB Tube Preamp - Manual (Page 7)

SIGNAL/CLIP LEDs
These LEDs provide a means of measuring the output signal levels required for the A/D converters and to prevent clipping. The
LEDs monitor both the signal present at the preamp (pre LEFT or RIGHT LEVEL control) as well as the A/D converter (post LEFT
or RIGHT LEVEL control).
Note: Reducing the Level controls to 11 O'clock or less will provide a signal level /clip indication of primarily the input section. Do
this to check and see if the LEFT or RIGHT GAIN controls are set too high.
MONITOR MIX knob
This controls the proportion of the preamp signal vs. the D/A signal from the computer (via the USB jack) present in the monitor
jacks. When fully counter-clockwise, only the preamp signal is present with the computer signal muted. When rotated fully clockwise,
only the computer signal is present in the monitor output jacks.
MONITOR LEVEL knob
This controls the master stereo output level present at the Headphone or Monitor Output jacks.
MONITOR HEADPHONES jack
The Headphones jack on the front panel is an unbalanced version of the Monitor Output jacks on the rear suitable for driving head-
phones over a 1/8" mini-phone jack.
STEREO/DUAL switch
This switch controls the preamp LEFT/RIGHT LEVEL controls. Stereo mode changes the two knobs from independent control over
the two outputs to a Master volume (left knob) and Balance (right knob). This is useful when you have a stereo input signal and need
to control the level of both inputs at the same time.
OPTO link switch
This switch ties the gain of each channel's Opto Compressor together. This is required when controlling stereo sources so the stereo
image is maintained.
MONITOR switch
Depressing this switch will sum both input channels together for the Preamp source of the MIX control. This is useful when recording
a single input and listening to it through both left and right headphone or Monitor outputs while listening to a stereo return from the
computer (via USB). This switch does NOT affect the signal presented to the A/D converter or the INSERT jacks.
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