XTA DS8000/D - Manual (Page 29)

Page 29 DS8000 Operator’s Manual
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Active Splitter with Transformer Isolation
The final solution addresses the problems inherent in passive transformer isolated systems
by using active circuitry to provide gain where necessary and local 48V if required. This is the
way the DS8000 works.
Mic Signal (~-40dBu) Signal
Ground
-10dBu
0dBu
0dBu
Local Ground
Local Ground
Local Ground
Outside
Broadcast
Truck
Front of House
Mixing Console
Monitors
Mixing Console
The low-level microphone signal is now fed through a gain stage that amplifies it to a
professional line level signal using a high quality microphone pre-amp. This immediately
means that all signals fed to other equipment will operate at line level, greatly reducing their
susceptibility to noise pick-up. Also, being line-level, there will be no need to add gain at the
desk, so there will not be the associated decrease in signal to noise ratio caused by the extra
gain.
The output drivers for each feed are also lower impedance so reducing the effects of cable
loading (the capacitative effect reducing HF content), resulting in a more accurate, flat
response. These electronically balanced buffered outputs also have earth lift switches, which
can isolate the ground connections if there are problems with hum loops.
The individual mixing desks are both fed from individual buffered outputs.
The OB truck is fed from a transformer-isolated output, itself running at line-level (-10dB) and
being buffered independently from the electronically balanced outputs. This galvanic
isolation ensures any separate grounding at the OB Truck will not introduce grounding
problems.
As the DS8000 is an active device, it can generate the 48V phantom power required for the
microphone inputs if required. It also senses 48V being switched in from a mixing desk and
can enable the respective input’s 48V supply if needed, providing seamless “echoing” of the
phantom power.