Studio Technologies 5401A, Руководство пользователя

Страница: 21 / 53

Model 5401A User Guide Issue 4, August 2021
Studio Technologies, Inc. Page 21
Model 5401A
DANTE LEADER CLOCK
transmitter (output) channels provide eight sine wave
tone labeled Tone 1 through Tone 8 . Changes to the
Dante sample rate are made using the Dante Control-
ler software application.
Type: This is a configurable field with three choices:
Word Clock, Video, or 10 MHz.
If the Model 5401A’s clock source has been selected
to Sync Input on the Main menu the type of connected
source must be defined to match the application. If
Word Clock is selected then a square wave source
with a rate of 44.1, 48, 88.2, 96, 176.4, or 192 kHz
needs to be connected. For proper operation the
nominal unloaded level of the word clock source must
be 5 volts DC peak-to-peak. Also, the connected word
clock source must match the displayed current Dante
sample rate. This is a bit of a “chicken or the egg” situ-
ation since it can be confusing as to who is supposed
to control the sample rate and who is supposed to
follow the sample rate! The Dante Controller software
application should be used to select the desired Model
5401A sample rate. This is the sample rate desired
for the sine wave audio channels provided by the
tone generator function. In most applications this will
be 48 kHz. It’s possible that in some audio-only ap-
plications 96 kHz or even 192 kHz will be selected.
Once the desired sample rate has been selected
and/or confirmed, an external word clock source of
the same rate should be connected. If the available
external word clock source has a rate different than
the current Dante sample rate then a review of the
entire application must be performed and a common
rate selected.
If Video is selected for the sync input type then a wide
range of bi- and tri-level video reference signals can
be connected to the sync input BNC jack. The Model
5401A’s circuitry will automatically decode many of
the most common format/rate combinations. These
include ubiquitous “black burst” signals as well as sig-
nals intended to support 4K video applications. Refer
to Appendix A at the end of this guide for a detailed
list of compatible video sources.
If 10 MHz is selected then the sync input is expecting
connection of a sinusoidal source of 10 MHz. A signal
of this type is typically associated with industrial or
instrumentation applications. It may also be provided
by a GPS (satellite) receiver.
If a choice of sync sources is available for a specific
application it’s recommended that a source of word
clock be utilized. This is not because a word clock
source is inherently better, but rather the recommen-
dation is related to the Model 5401A’s circuit design.
The unit’s logic circuitry has to perform the least
amount of processing with a word clock input signal
as compared to that required to utilize a video refer-
ence or a 10 MHz signal. All compatible signals will
work well but using a source of word clock requires
the least logic “horsepower.”
Termination: This is a configurable field with two
choices: Off and On.
If desired, the Model 5401A can apply a terminating
impedance to the sync input connection. The need for
an input source to be terminated, or not, will depend
on the source of the external sync signal. Typically,
a source of sync should have one (and only one)
termination applied. A timing reference source can
generally be shared (“bused”) to multiple devices
with only the last connection on the “string” having
an appropriate termination.
If the sync input termination is configured for Off then
the sync input’s impedance will be considered “high
Z.” If the sync input termination is selected to On and
the sync input type is selected for Word Clock or Video
the termination impedance will be 75 ohms. If 10 MHz
has been selected as the sync input type then a ter-
mination impedance of 50 ohms will be applied.
These termination values were selected to meet the
technical requirements of industry-standard reference
signals. Word clock should be a square wave with a
source impedance of 75 ohms. Video is typically a
complex analog signal with a source impedance of 75
ohms. And a 10 MHz reference is a normally a sine
wave with a source impedance of 50 ohms.
Submit: A Submit button is located on the bottom of
the Sync Input menu webpage. To save any changes
made to fields on the Sync Input webpage requires
that the Submit button be pressed. The Model 5401A
will immediately incorporate operating changes as
soon as the Submit button has been pressed.