User Guide

Issue 4, December 2020 Model 780-01/790 User Guide
Page 10 Studio Technologies, Inc.
for Surround
There is, however, an exception worth
noting. Circuitry associated with the stereo
input has sample rate conversion (SRC)
capability, allowing virtually any stereo digi-
tal audio signal to be connected. A signal
connected to the stereo input can have an
independent sample rate and timing refer-
ence while still being monitored correctly.
Refer to the Technical Notes section of this
user guide for a detailed review of the SRC
capability.
The Model 780-01’s audio inputs are in-
tended for connection with balanced digital
audio sources that are compatible with the
AES3 standard. This type of signal has
a nominal impedance of 110 ohms and a
nominal signal level of 5 Vpp.
One 25-pin female D-subminiature con-
nector (DB-25F) is used to interface with
the 16 channels associated with surround
input A and surround input B. Each of
the eight connections supports two audio
channels. Often a wiring assembly pre-
pared for these digital audio inputs would
be identical to that of a TASCAM®-type
(AES59-compliant) input assembly. A typi-
cal assembly of this type will often have
eight 3-pin female XLR connectors on one
end and a 25-pin male D-subminiature
connector (DB-25M) on the other. Refer
to Figure 4 or Appendix A for details on
connecting with the 25-pin female D-sub-
miniature connector.
Note that unlike a TASCAM-type assem-
bly, the two threaded fasteners associated
with the Model 780-01’s D-subminiature
connector use 4-40 threads. This complies
with the original design standard for D-sub
connectors.
On the Model 780-01 the stereo input uses
a 3-pin female XLR connector for interfac-
ing with a digital audio source. The mating
cable should have a 3-pin male XLR con-
nector wired such that the + signal goes
to pin 2, the – signal to pin 3, and shield
to pin 1.
Unbalanced AES3 digital audio signals
can also be used with the Model 780-01’s
inputs if external coupling transformers
(“baluns”) are utilized. These impedance-
matching (75 ohms to 110 ohms) and level
step-up transformer assemblies typically
provide a BNC connector on their input
and a 3-pin male XLR connector on their
output.
Monitor Outputs
The 25-pin female D-subminiature con-
nector on the back panel labeled Digital
Monitor Outputs provides access to the
Model 780-01’s pre- and post-fader digi-
tal audio monitor outputs. The channels
are organized as two 8-channel surround
(7.1) sources, one pre-fader (fixed level)
Signal Signal
Connections Channel High (+) Low (–) Shield
Surround Input A
L/R 1 24 12 25
Surround Input A
C/LFE 2 10 23 11
Surround Input A
SL/SR 3 21 9 22
Surround Input A BL/BR 4 7 20 8
Surround Input B L/R 5 18 6 19
Surround Input B C/LFE 6 4 17 5
Surround Input B SL/SR 7 15 3 16
Surround Input B BL/BR 8 1 14 2
Notes: 1) All signals transformer-coupled digital audio;
balanced AES3 (110 ohms, 5 Vpp) compatible.
2) Connector type on Model 780-01 is 25-pin female
D-subminiature (DB-25F). Installer must provide male
(DB-25M). Connector uses 4-40 threaded inserts for
locking with mating plug.
3) Wiring scheme follows AES59-2012 convention.
Standard TASCAM-type wiring harnesses are directly
compatible, with the possible exception of 4-40 screw
threads being required.
Figure 4. Connections for Surround A and
Surround B Digital Inputs