Cadac CDC four - Manual (Page 31)

Revision 1 2012-13 CDC FOUR
31
Audio channel descriptions
Input channel
A detailed block diagram of the Input channel may be found in the Appendix on
page 74.
The CDC FOUR can handle up to 48 mono mic/line inputs, divided into three
blocks of 16. The inputs to Channels 1 to 16 are on the rear panel; those for
Channels 17 to 48 are only available if the CDC RACK stagebox is in use.
The CAM and the TFT display are made active for a mic/line input when one
of the first three layers is selected (CHNS 1-16, CHNS 17-24, CHNS 33-48).
The active channel is that whose SEL button is illuminated. If no CDC RACK is
connected, the two buttons CHNS 17-32 and CHNS 33-48 will be inoperative.
Mic pre-amps
Mic/line inputs 1 to 16 are equipped with high-quality, low-noise mic pre-amps.
This design uses premium ICs and exhibits wide dynamic range and excellent
CMRR. The gain control operates in the analogue domain, and has a range of
0 to +60 dB.
Meters
The 10-segment LED bargraph meter shows either the pre-fade or post-fade
signal in the channel, as selected by the Pre/Post switch on the METERS screen
page. The sixteen fixed meters (below the mic pre-amp gain controls) change
source with layer selection, thus can be used to monitor stereo inputs, group
and Aux sends, etc., as well as mic/line inputs. When the ST CHNS VCA layer is
selected, the odd numbered meters show the left legs of the stereo channels, and
the even-numbered the right.
The lowest LED (coloured green) illuminates at -54 dB and can be considered
a “signal present” LED. The top three LEDs (coloured red) illuminate at -6 dB,
-3 dB and 0 dB respectively. Note that the 0 dB reference for these levels is
0 dBFS (digital clipping). Thus the input gain should be adjusted so that the top
LED never illuminates.
MIC 1
60 0
0
3
6
9
12
15
18
24
36
54