DiGiCo SD Rack - Manual (Page 7)

SD Rack
1-7
1.4.1 Analogue Mic/Line Input card (ADC) ..................................
The 8 Mic/Line input ADC card has 2 indicators on each socket.
The orange indicator shows the status of +48V Phantom Power On/Off.
The green indicator shows signal present and this turns red when the signal is close to clipping.
1.4.2 Analogue Line Output card (DAC) ......................................
The 8 Line output DAC card has 2 indicators at the bottom of the card.
The red indicator shows the status of Gain Tracking On/Off.
The yellow indicator shows the status of the card Split On/Off.
1.5 Splits & Gain Tracking
1.5.1 Split Options ........................................................................
The SD Rack has several different Split options.
1) Each input slot (block of 8 sockets on an input card) can be split to its relevant output slot. So slot 1 would be split to slot 8, slot 2 to
slot 9 and so on. These split signals can be automatically Gain Tracked so that any change in the analogue gain on the input socket is
compensated by the opposite change in digital trim on the relevant output socket.
The output cards have LED indicators showing Split ON/OFF and Gain Tracking ON/OFF status.
2) There are 2 dedicated MADI split ports on BNC connectors labelled MADI Split Main (MadiSM) and MADI Split Aux (MadiSX).
These ports can provide either 2 independent split signals at 48KHz or a pair of split signals that contain MADI channels 1-28 and 29-56
at 96KHz.
These outputs can also have automatic Gain Tracking applied to them on a per split basis. Eg. Main Split with Gain Tracking On and Aux
Split with Gain Tracking Off
1.5.2 Gain Tracking .......................................................................
Gain Tracking can be controlled from the Rack LCD Menu system or optionally by an SD Series console.
With Gain Tracking switched ON the digital trim on the split outputs works in direct relation to the analogue gain that is applied to the
relevant (same numbered) input socket. Any change in the analogue gain at the input results in the opposite change being applied to the
digital trim of the output split socket.
If the analogue gain of an input socket starts at 0dB and with Gain Tracking On is raised to +10dB, the output split level will remain
constant because it will have had a -10dB change applied to it in real time.
The correct procedure to follow is to set an acceptable level of analogue gain on each input before switching the Gain Tracking function
on. Once the Gain Tracking function is active it should not be switched off without careful consideration.
There is also a Gain Track Reset function which sets the split output digital trim to zero. This function should also be treated with due care
because using it on an active split will potentially change the output level by a large amount.