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Author Topic: Avid Mix Rack - Clear Com  (Read 5479 times)

Geoff Doane

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Re: Avid Mix Rack - Clear Com
« Reply #10 on: December 20, 2012, 09:58:09 pm »

Even the 12V supply needs to be regulated down to 5V to get under the 5.5V maximum voltage on the GPI.

Mac

The maximum spec for the GPI input is 5.5V, but it is an active low, with an internal pull-up resistor to its internal 5V.  Applying 5V to the input won't do anything.  It's looking for a ground to change state.

I'd probably use an opto-isolator for this, since they're small, cheap, and fairly tolerant of different input voltages.  The quick drawing below shows a suggested hookup diagram for the first one I found a data sheet for in a Google search.  If you're not familiar with these, a current flowing through the LED will cause the transistor to conduct.  The light from the LED acts as the base of the transistor.  In this case, 12V on the input will give you about 2 mA through the LED.  The minimum current transfer in the device is 50%, so that will cause 1 mA to flow through the output side, which is enough to drag the 5V on the GPI input (held up by a 5K resistor) down to 0 V, and the input will be active.

The resistor value is not very critical.  It really just needs to limit the current to something less than what the LED can withstand, which is 50 mA.  The same circuit could handle 24, or even 30V at the input without anything blowing up.  And because it uses an opto-isolator, there's no danger of contaminated grounds anywhere, or relay coil transients.

GTD
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Al Rettich

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Re: Avid Mix Rack - Clear Com
« Reply #11 on: December 20, 2012, 11:44:35 pm »

Please do tell a bit more.. I'd like to learn. What & where do I get a EF701?
The best way to do this is via a 2-4 interface, for a number of reasons:

First, something like a EF701 allows you to not only send call signalling into the console, but also allows your monitor engineer to talk to and listen to the comms channel via the desk. This is very useful as it allows you to have a combined talkback & comms environment where the engineer can keep his IEMs in and use a single talk mic.

Secondly, an EF701 has a bunch of other uses (like interfacing with radio systems)
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Al Rettich

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Re: Avid Mix Rack - Clear Com
« Reply #12 on: December 20, 2012, 11:50:46 pm »

Is there a website that teaches you about GPI? It's something I knew the consoles had, but was never really shown, or taught about. Now I want to try and take some initiative and learn about it.
Hey everyone. I hope all are getting ready for a great Christmas.

I'm finishing up a string of dates mixing FOH and we did a fly date yesterday and I saw something I had never seen before. Wondering how and if any of you knew how to do it.

The systems guy mixed the opening act and I saw that set up behind him was a TP beltpack system with a flasher. When the flasher went off his console lights blinked on and off.

Sadly, I never dealt to deep on the events of the Avid system but I want to include that on our next run. I like it. So, anyone know how he did it??
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Mac Kerr

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Re: Avid Mix Rack - Clear Com
« Reply #13 on: December 21, 2012, 12:12:49 am »

Please do tell a bit more.. I'd like to learn. What & where do I get a EF701?

The Clear Com EF-701 4 wire adapter should be available from any Clear Com dealer. Using 4 wire interfaces is pretty common in high level intercom, like TV comm. If you are running comm very long distances you can turn the unbalanced powered comm channel into an unpowered balanced send and return. This will keep induced noise down, but will require a power supply at each end. By making an balanced line level in and out, you can also interface the comm to other audio gear, like a console.

Matrix comm systems like Riedel Artist, RTS Adam, and Clear Com Eclipse, are all based on routing balanced audio, and operate in 4 wire mode all the time. To use a 2 wire system like Clear Com beltpacks you need to use a 2W-4W interface. In TV there are often many channels of 2W-4W conversion going on.

The EF-701 is a single channel device, for more channels CC has the CCI-22 card that goes in a card frame for up to 11 two channel interfaces in 3RU.

Mac
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Mac Kerr

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Re: Avid Mix Rack - Clear Com
« Reply #14 on: December 21, 2012, 12:16:23 am »

Is there a website that teaches you about GPI? It's something I knew the consoles had, but was never really shown, or taught about. Now I want to try and take some initiative and learn about it.

Ii don't know of a website, but any console that has GPI (General Purpose Interface) ports should have a list in the manual of what functions can be controlled from the GPI ins, and how you can trigger the GPI outs. The ins are often used in theater for an external GO button to select the next scene. The GPI outs can be used to start a playback machine from a UDK, or a scene change.

Generally they operate at TTL levels, with both high and low triggers that you select in software.

Mac
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kristianjohnsen

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Re: Avid Mix Rack - Clear Com
« Reply #15 on: December 21, 2012, 03:56:11 am »

Ii don't know of a website, but any console that has GPI (General Purpose Interface) ports should have a list in the manual of what functions can be controlled from the GPI ins, and how you can trigger the GPI outs. The ins are often used in theater for an external GO button to select the next scene. The GPI outs can be used to start a playback machine from a UDK, or a scene change.

Generally they operate at TTL levels, with both high and low triggers that you select in software.

Mac

Also used in studios to trigger red lights by doors, etc.  I know some broadcast studios have GPI router matrixes bacause different techs use so many different options.
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Chris Johnson [UK]

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Re: Avid Mix Rack - Clear Com
« Reply #16 on: December 21, 2012, 04:18:25 pm »

Also used in studios to trigger red lights by doors, etc.  I know some broadcast studios have GPI router matrixes bacause different techs use so many different options.

Yes. When I'm not mixing FOH, I build and operate larger matrix intercom systems for live events.

"Proper comms" systems have GPI functionality built into the matrix, so typically I would setup the intercom matrix to handle all the audio routing for everything that isnt the FOH or Mon mix, and include in that any necessary signalling between devices. Its perfectly possible to implement a Cue light system through a matrix intercom.

One of my next projects will be to create a simple way of triggering a Clearcom/ASL beacon via a GPO and a simple PSU. This would allow me to implement shout systems that are routed through a matrix or consoles, but that still retain strobe functionality for users who aren't in constant listen (like FOH engineers...)

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Riedel Communications

David Buckley

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Re: Avid Mix Rack - Clear Com
« Reply #17 on: December 21, 2012, 07:07:26 pm »

Even the 12V supply needs to be regulated down to 5V to get under the 5.5V maximum voltage on the GPI

The relay takes care of that; as others have noted, the GPI requires contact closure to ground, rather than a voltage feed.  As the GPI input is already held up to 5V then supplying 5V to it won't cause it to switch state.

Geoff has suggested usin an opto isolator, and that would also work nicely, but for folks not used to soldering around a the chip level, a relay is much less challenging :)
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