Grass Valley SMS-6000 Series - Manual (Page 22)

1-5
Analog Audio Routing
Analog Audio Routing
In the 1RU frame, the main analog audio matrix module provides a dual
channel 16x16 matrix. The 16x4 stereo audio is also a 1RU frame. This
matrix fits in a 1RU frame, which supports only a single power supply.
In the 2RU frame, two 16x16 matrix modules are used to make a 32x16
matrix. The main (lower) audio router module routes inputs 1–16 and the
submodule inputs 17–32. The output stages and their gain adjustments are
installed on the (upper) submodule for accessibility. Two 32x16 pairs of
modules are used to build up a 32x32 mono audio matrix. Dual power
supplies can be installed in this frame. Two frames are used for stereo.
Inputs
The inputs are electronically balanced. This provides a high common mode
rejection ratio over a wide frequency range. Also, the balance is maintained
even if the source is floating. Some designs of electronically balanced
inputs cause the input lines to become unbalanced which can cause an
increase in crosstalk if the input cables are unscreened and run together
over long distances.
The input and output connectors are 50-pin D connectors.
The signals are filtered to reduce out-of-band high frequency signals and
re-balanced for internal use. The use of balanced circuitry throughout is of
immense value to the overall quality of performance. It improves virtually
every measured parameter by at least a factor of 2 compared to a similar
unbalanced design.
Crosspoints
The matrix uses balanced 4x4 crosspoint chips. These exhibit excellent
signal path performance together with minimal crosstalk and switching
noise.
Outputs
The only adjustment in the audio path is the output gain control. It offers a
±
2dB gain control and is mainly provided to allow the gain to be adjusted
up slightly if the outputs are terminated in 600
Ω
. As this is now an unusual
practice, the insertion gain is factory set for unity into a load of 10k
Ω
.