Crystal Vision
Card edge operation
TANDEM HD-20 User Manual R1.4
22
24/05/2007
16x8 routing matrix
At the heart of TANDEM HD-20 is the sixteen input, eight output routing matrix. This
will allow any of the sixteen possible inputs, eight embedded channels and up to eight
analogue or digital audio inputs to be routed to any of the eight outputs for embedding or
to be outputted via output sub-PCBs. The final configuration will depend on the number
and type of sub-PCBs fitted.
Note: Front and Rear describes the position of the sub-PCB when fitted to the TANDEM
HD-20. Front nearest the board edge controls and extraction handle. Rear nearest the
board connector.
Note: If an output sub-PCB is fitted to the front position its output will always follow
embedder C routing. Similarly a rear fitted output sub-PCB will always follow embedder
D routing.
Stereo to Mono conversion
For the purposes of this discussion it is assumed that all inputs are stereo pairs and that
each half of the stereo pair is on a consecutive input i.e. input 1 and input 2 are a stereo
pair, input 3 and input 4 are a stereo pair, etc.
The action of converting a stereo pair to a mono output is simply a summing process
followed by a gain correction. The gain correction is necessary because when the two
components of a stereo signal are summed a 6dB increase in output level will result; this
will then need to be corrected to maintain unity gain.
The action of selecting will cause that channel to output the mono sum of itself and its
associated channel. The associated channel output will still output its unaltered
programme. Either channel of a pair can be selected for stereo to mono conversion.
Example: Selecting channel 1 for mono conversion will result in channel 1 outputting the
converted mono sum of channels 1 and 2. Channel 2 will remain outputting the original
channel 2 programme. Similarly deselecting channel 1 and selecting channel 2 will cause
channel 2 to output the converted mono programme and channel 1 the original channel 1
programme.
Delay control
This control can be used to delay the audio with respect to the video by up to 64ms and
compensate for any small delay between the incoming video and audio signals. The delay
is applied at the output of the 16x8 router and is a single global control. The delay can be
added individually to any output channel.
Individual channel can also be selected to mute.
