AUDIO OPERATIONS 4-7

Send Level Controls

The three large black knobs control the level of their respective signals to the send bus.
They are calibrated in arbitrary gray dots that don’t mean much, since the best way to
mix is by using your ears and the SEND meters.

SEND Meters

The two 14-segment SEND level meters have a fast attack and slow decay time, to alert you
to any problems in the transmitted level. They monitor the signal as it enters the audio
encoder, which works best when it’s got reasonably high levels to work with. Adjust the
mixer so that most of the green LEDs are lit during average program material, with the
red ones flashing occasionally.
Heavily-compressed material, such as pre-recorded commercials and popular dance
music, can be set to average in the red area as long as the OdB segment isn’t lit. Zero is the
clip point, and there just isn’t any headroom above it.
-30 -20 -10 0dB

CH A

CH B

SEND

tDIGITAL AUDIO TIP!
You’ll notice that normal operating level is around -10dB and zero is at the top of
the scale. This is different from analog VU and deciBel meters you may be used
to, but it’s standard practice on digital devices.
The reason is that analog equipment has a few dB headroom above the normal
“zero” level (and zero itself is arbitrarily matched to a particular voltage,
magnetic strength, or modulation). Digital equipment, on the other hand,
counts deciBels down from absolute full scale —the condition where all bits are
turned on — and there just isn’t anything that can be louder that that.
hHOT TIP!
The meters don’t operate on channels that are in standard telephone / G.711
mode. During Far Loopback test mode, both meters are off and the center
segment is lit as a reminder that normal operation is disabled.