© 2010 Wohler Technologies, Inc. All rights reserved.
9
SUM Series User Guide
Front Panel Controls
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Input Source Volume Control
(1 through 8): Each of these volume
controls affects the loudness of only the selected audio source for
the channel it is associated with (1 through 8). Channel numbers are
silk-screened above each control. When the unit is set for mono
operation, all channels are summed together (at their respective
levels) monaurally across both speakers. When set for stereo
operation the left speaker reproduces the mix of channels 1, 3, 5, and
7 and the right speaker reproduces the mix of channels 2, 4, 6, and 8.
Mono or stereo operation is selected by placing the 4-wire audio
harness on one of two headers internal to the unit.
Note that the Input Source Volume Controls are positioned so that
when operating the unit in stereo mode, the volume controls for
channels 1/2, 3/4, 5/6, 7/8 are arranged in four left/right pairs.
These pairs also correspond to the AES input channel pair
designations of A, B, C, and D.
Digital Gain Calibration for each of the eight AES audio source
channels is adjustable, allowing calibation relative to the analog
input levels. Digital gain calibration is accomplished by adjusting
eight trim-pots internal to the unit. Digital gain calibration is factory
set at -20 dBfs digital to +4 dBu analog for all eight channels. See
page 10 for setting instructions.
A Mute on Data feature is available allowing the unit to mute any of
the four AES inputs when a datastream (i.e. Dolby) is detected at the
AES input. Factory setting is for this feature to be activated. See
page 10 for setting instructions.
The unit may be configured (with internal jumpers) to mute the AES
input(s) and indicate an error (A/D Input Select Button glows red
on front panel) when a set validity bit is detected at the input(s).
Factory setting is for this feature to not be activated.
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A/D Input Select Buttons and AES Input/Lock Indication LEDs
(1 through 8): Each of these buttons is used to select the source
signal for the associated channel. Channel numbers are silk-
screened below each button. Each button features an integrated bi-
color LED (green/red) used for button status indication. When an
analog source is selected, the button is unlit. When a locked AES
source is selected the button glows green. When the selected AES
