Studio Technologies 770 - Manual (Page 12)

Issue 1, October 1997 Model 770 User Guide
Page 12 Studio Technologies, Inc.
Model 770
connection to sources located within
the vehicle, specifically the audio output
channels of videotape machines. Note that
the left and right inputs associated with the
stereo line inputs are always mixed, by
way of level controls, to monaural. The
electronically balanced input circuitry has
extremely low noise and high common-
mode rejection, but no extra protection
from overvoltage or static. (Don’t get us
wrong—the stereo line input circuitry is
better than what’s found on most audio
mixers available today—they’re just not as
“tough” as the mic/line inputs!) The stereo
line input circuitry is intended for connec-
tion to balanced or unbalanced, line-level
signals with a nominal operating level of
+4dBu.
Each stereo line input channel uses two
¼-inch 3-conductor phone jacks. Prepare
the mating connectors (plugs) so that tip
is signal high (+ or hot), ring is low (– or
cold), and sleeve is shield. With an unbal-
anced source connect the tip to high
(+ or hot), and both the ring and sleeve
to shield. If connecting to an unbalanced
source in this manner results in hum or
noise, connect tip to high (+ or hot) and
ring to shield; leave the sleeve untermin-
ated. For flexibility of use it is recom-
mended that the stereo line input con-
nections be routed through points on a
patch bay.
Main Outputs—General Information
The Model 770 contains four outputs
associated with the main audio bus. Main
Outputs 1, 2, and 3 are electronically
balanced, have a nominal level of +4dBu,
and are capable of driving balanced or
unbalanced loads of 600 ohms or greater.
The unit is secured to the front mounting
rails of an equipment rack using two
mounting screws per side.
Connections
The Model 770’s input, output, and
telco connections are made using 3-pin
XLR-type male and female connectors,
¼-inch 3-conductor phone jacks, and one
6-position modular telephone-type jack.
Caution: For reliable audio intercon-
nection, the phone plugs you use must
comply with industry-standard RS-453.
Switchcraft No. 297 or Neutrik NP3C
are highly recommended.
Mixer Section
Mic/Line Inputs
The Model 770 contains three input chan-
nels that are compatible with microphone
or line-level sources. Each of the three
Mic/Line inputs use a single 3-pin female
XLR-type connector. Prepare the mating
connectors (males) so that pin 2 is signal
high (+ or hot), pin 3 is low (– or cold),
and pin 1 is shield.
It is expected that the mic/line inputs will
be wired to an input/output connector
panel located on the side or rear of the
vehicle. It’s also nice to have one or two
of the inputs “multed” to connectors inside
the vehicle, allowing the rapid connection
of microphone or line-level signals. To
minimize noise and other problems, it is
recommended that the mic/line signals
are not wired by way of points on an audio
patch bay.
Stereo Line Inputs
The Model 770 contains two stereo line-
level input channels. They are intended for