User Guide

Model 76D/77 User Guide Issue 13, December 2020
Studio Technologies, Inc. Page 47
for Surround
Error Code Err4
Err4 will display if communications with
a central controller has been established
but that specific central controller is not
compatible with the Model 77. For ex-
ample, Err4 will display if a Model 77 has
been connected with a Model 780-Series
central controller.
Sample Rate Conversion
(SRC)
Circuitry associated with stereo input C
can provide sample rate conversion (SRC)
capability. A digital audio signal connected
to that input can have its sample rate and
timing re-synchronized to match the Model
76D’s internal timing. While it would be
nice to proclaim that the engineers at
Studio Technologies came up with a
unique and exotic circuit to perform this
function it’s really not the case. Several
semiconductor companies provide “single-
chip” SRC solutions and an excellent one
from AKM was selected for the Model
76D. The technical capabilities of the
Model 76D’s SRC function is stated in this
way: the sample rate of an input signal
can range from 1/6 to six times the Model
76D’s output sample rate, with the ad-
ditional restriction that it must be no less
than 8 kHz and no more than 216 kHz.
The Model 76D’s output sample rate is de-
termined by the selected timing reference
(sync) signal and, if required, a configured
value. If a word clock, DARS (AES11), or
AES3 signal is the designated sync source
its rate will be the Model 76D’s output
sample rate. If a video sync signal is con-
nected, the Model 76D’s sample rate is se-
lected as part of the configuration process.
So in practice what can the SRC function
accomplish? If the output sample rate is
48 kHz then a signal connected to stereo
input C can have a sample rate from 8 to
216 kHz. Or, as another example, if the
Model 76D’s output sample rate is 96 kHz
a signal connected to stereo input C can
have its sample rate range from 16 to
216 kHz.
As useful as allowing one disparate
sample rate to be converted to another,
it may be the ability of the Model 76D’s
SRC function to re-synchronize a signal
that proves most valuable. For example,
in typical post-production and broadcast
applications all signals will have a sample
rate of 48 kHz. A Model 76D and all of its
normally connected input signals will be
“locked” to the main timing reference sig-
nal that supports the 48 kHz sampling rate.
But, as an example, a signal associated
with a portable device, while at a 48 kHz
sampling rate, may not be synchronized
(“genlocked”) to the “house” reference.
Connecting this signal to stereo input C
will cause the SRC function to “lock” it to
the Model 76D’s rate, thus allowing it to be
monitored over a loudspeaker system. In
addition, the stereo input C direct monitor
output can be connected to other devices
that find need for the now-synchronized
signal. In some cases it may be useful to
connect the stereo input C direct monitor
output to the input of a signal router, allow-
ing an entire facility to access the signal.
Model 76D to Control Console
Connections
Figure 6 gives a detailed description of the
signals that connect the Model 76D Cen-
tral Controller to the one or more Model 77
or Model 71 Control Consoles. The Model