Aes Signal Ground Isolators - Pacific Microsonics HDCD Model Two User Manual

Installation
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Model Two HDCD User's Manual
For best performance, AES3 cables should have the chassis ground path isolated by a series
100 resistor. Use of a low capacitance isolation transformer at the Model Two's AES
signal inputs, or the AES Signal Ground Isolator described below at both inputs and out-
puts is also recommended. Cables sending AES3 or synchronization signals from the Model
Two to other equipment should have transformer isolation placed at the inputs of the
receiving equipment. If external transformers are used they should always be at the receiv-
ing end of the digital signal path and never at the transmitting end.
The Word Clock Ref Input/Output uses a BNC connector with its shield isolated from chas-
sis ground. An external 75 terminating resistor must be used when Word Clock Ref is in
input mode. This allows a high impedance loop-through connection. When configured as
an output by selecting Reference Clock Master Mode (SETUP/INPUT/REFCLK/MASTER), the
Word Clock Ref connector outputs a special AC coupled word clock. See pages 26 and 27 for
more information. BNC word clock cables should not use low capacitance isolation trans-
formers because they are unable to pass TTL level signals.

AES Signal Ground Isolators

Pacific Microsonics AES Signal Ground Isolators are designed to break ground loops which
can occur between the grounds of digital and analog signal cables when they are con-
nected together by a single device that has both digital and analog signal connections,
such as the Model Two HDCD Processor. If not properly isolated, noise currents on grounds
have the potential to seriously degrade A to D and D to A converter performance.
The AES Signal Ground Isolators should be connected to all AES digital signal inputs and
outputs at the Model Two whenever they are in use. The AES Isolators are designed to be
used in series with standard AES cables that are connected to digital recorders, editing
workstations, etc. Four Isolators are provided with each Model Two.
The AES Ground Isolators consist of a number of turns of precision 110 balanced, shielded
cable fed through multiple ferrite cores, each having a different selected permeability. The
cable is terminated with XLR-3 connectors. This construction provides 160 H of inductive
filtering effective over a very wide range of frequencies. A 100 resistor is also placed in
series with the pin 1 ground connection, providing further isolation.
Note: Pacific Microsonics recommends that as general practice, a 100 resistor should be
installed in series with the pin 1 (shield) connection at the female connector end of all
AES cables to reduce the potential of digital ground loop noise.
P A C I F I C M I C R O S O N I C S I N C .
Rev. C - January 2002
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