Studio Technologies 42A 2008 - Manual (Page 9)

Model 42A User Guide Issue 2, February 2008
Studio Technologies, Inc. Page 9
Audio Input Connections
The Model 42A has eight line-level audio
inputs, arranged as four 2-channel pairs.
Each pair serves one of the four IFB cir-
cuits. Each IFB circuit, along with its two
associated audio inputs, is completely
independent. Literally any audio source
with a nominal operating level in the range
of +4 dBu can be successfully connect-
ed. Transformer coupled, the inputs are
compatible with balanced or unbalanced
signals. In many applications the analog
outputs from digital matrix intercom sys-
tems will be connected to the Model 42A.
For on-air television applications the IFB
sources are generally configured to pro-
vide a single- or dual-channel cue “feed”
to talent personnel. In such cases channel
one of a pair is generally designated as
the “interrupt” channel while channel two
is the “program” channel. For other broad-
cast applications, such as live radio, it’s
possible that a stereo cue source will be
connected. In this situation the left source
would be connected to input channel one
while the right source would be connected
to input channel two. This might also be
the case with other professional audio
applications, such as recording and post-
production.
Figure 1. Detail of back panel showing connector used for audio inputs
Audio input connections are made by
way of one female 25-pin D-subminiature
connector which is located on the Model
42A’s back panel. A cable harness is
required with a 25-pin D-sub plug (male)
on one end and the desired mating con-
nectors on the other. This cable harness
is not supplied by Studio Technologies.
(Note that in some locations the term
“cable loom” may be used instead of
“cable harness.”) The wiring scheme
used by the D-sub complies with the
now-ubiquitous one made familiar by
TASCAM® with their DA-88® product. A
wiring harness prepared for connection
to the Model 42A’s audio inputs is identi-
cal to a DA-88-style input harness. Please
refer to Figures 2 and 3 for connection
details. Note that unlike a DA-88-style har-
ness, the Model 42A’s D-sub connector’s
hold-down screws use 4-40 threads. This
complies with the original design standard
for D-subminiature connectors which used
English rather than metric thread pitch.
The Model 42A’s audio input circuits have
a nominal signal level of +4 dBu. They
are transformer coupled, have a nominal
impedance of 10 k ohms, and compatible
with balanced or unbalanced sources.
Balanced sources should be wired so that
signal high is connected to the + pins,
signal low to the – pins, and shield to the