A P P E N D I C E S
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WheatNet-IP
/ Apr 2009
Category 2: Audio Associated Logic
There are many logic functions that are associated with or tied to specific audio
signals. You may have a START or a STOP logic function that associates with a
specific CD player or Automation machine, or ON and OFF logic functions that
associate with a control surface fader channel. In the good old days you would have
to wire a multi-conductor control cable from the logic ports on the machine to the
logic ports on your console. Once you were done, those logic connections would
only work for that one machine and one fader channel; if you patched your audio
to a different channel, the logic wouldn’t work right anymore. For this reason (and
to make it easier to set it all up in the first place), general practice was to wire all
of these connections up to punch blocks so connections could be changed via punch
downs rather than rewiring complicated multi-pin connectors.
It’s much easier with the WheatNet-IP system. First of all, many devices
(including Wheatstone control surfaces) now support logic control directly over
Ethernet connections, so separate logic wiring isn’t needed. For that equipment
that still requires physical logic connections, WheatNet-IP devices provide 12
available logic connections on every BLADE, and the system provides for audio
associated logic. That means the only physical wiring you’ll need for these devices
is a direct connection from the device logic connector to the RJ-45 jacks on a
BLADE.
Here’s how it works. Each audio signal within the WheatNet-IP system - that’s
every source and every destination including control surfaces - can have up to 12
different logic functions (from a list of 500 different types) associated with it.
Whenever an audio crosspoint connection is made between a source and a
destination, the system looks for matching logic functions (for example START
and STOP). For every matching function, a virtual logic connection is established
such that the logic input will control the logic output. If the audio connection is
changed, the system looks for matching functions in the new connection. In this
manner the logic functions are associated with or attached to the audio devices, and
hence follow with whatever audio connections are made.
This makes it easy to enable complex logic functionality without a lot of
physical wiring, and minimizes the need for punch blocks or other cross connect
and fan out wiring devices.
For an example, let’s set up our system so that a control surface ON button will
start a Denon DNC620 CD player. This machine has a D-sub 25 logic connector,
with a START function located on pin #9 and Command Common located on
pin #23. A momentary connection between pins 9 and 23 will cause the machine
to begin playback. Let’s assume that the CD player is located in our Air studio,
which has an E-6 control surface and e engine BLADE #4, and 88a analog
BLADE #5. We’ll say that the CD’s stereo audio output is connected to stereo
input 7 on BLADE #5 and we have given this source signal the obvious name
“CD.” Let’s further assume that we have already used the first logic port
connection on this BLADE for our ON-AIR warning light, so we want to use the
second logic port connection, pin #3, to START the DNC620. Your system will
likely have different BLADE and port numbers than these in the example; just
substitute your ID #s as necessary.
