Comms to Sound Desk

[Jambo_UK]

Hi all,

 

I have been given the task to research a way to connect a comms system (Tecpro/ASL) system to a sound desk. Searching this forum I have came up with people trying to do the other way round which is to put audio into cans.

 

Looking at some of the solutions for that issue I was wondering if it could be done in reverse to help me. I'm looking at a Female 4 pin XLR connector to 1 Male XLR 3 pin male and 1 female XLR 3pin. In the form of a Y splitter.

 

Like this from canford, http://www.canford.co.uk/commerce/productd...roductid=27-908

 

But I was wondering if this would work as the headphone feed would have power on it and putting it into an XLR socket could do damage to the desk without a resister in place to try and kill the excess off.

 

So now the question, Does anyone know a better solutions or know if the above will help.

 

Thanks in advance,

 

Jambo

 

PS> This is being used for a production of stepping out, where the crew can be heard over the PA to buy tiem for a quick change (2mins) ** laughs out loud ** Seems a lot of work for what it is. It is also so Comms can be recorded during a show as I work in one theatre and the conversations on comms are priceless and I would love to record them and so would some of the other techs there, speciality during panto.

[James]

Sounds like you need a 2wire to 4 wire convertor (AD903)

 

Much nicer solution than splitting the headphone cable.

 

James

[paulears]

much nicer, and vastly more expensive.

 

There isn't any problem with feeding tecpro kit into and out of a mixer, but you have a couple of ways you can do it. As you mention, you can simply split the 4 pin from the belt pack and feed the headphone level into an input. Depending on your kit, this usually works fine to get audio into the desk. Tecpro do have a few 'issues' with their pin 1 ground. Sometimes when you ground at the desk, a major ground loop hum starts. They do recommend that their system is not used with common grounds, so I expect this is something that is quite common (pun intended). You can DI it via a box or, if your desk has adequate mic amp pads, simply wire it via pins 2 and 3, ignoring the ground. I've found this is the simplest system on most desks I use. You then get your comms line into the desk which you can listen via the pfl/solos. I've got a beyer DT108 which is wired with a stereo jack and the mic output wired to the belt pack.

 

One thing to watch is that the audio input to the tecpro is a little more 'finicky'. Extra cable, unusual mic impedances etc can make the input circuitry unstable, resulting feedback style screaching. Careful adjustment of the side-tone can minimise, but sometimes not get rid of these problems.

 

Open circuit, or short circuit mic inputs can result in full level tones, so beware.

 

 

If you want, you can take the audio line and insert this into the desk. Via a DI box is best. The audio line level is ok direct into the desk, but bearing in mind the possibility of a wrongly wired cable shoving the dc power where you don't want it, going via a di box is pretty sensible.

 

The major snag (or benefit) of doing this, is that bringing up the wrong fader can add the comms line to the show audio - and depending on the singing abilities of the crew, can be a good (or in most cases) a bad thing! Handy during rehearsals, when the director, if cans enabled, can bellow at everyone.

[Jambo_UK]

The major snag (or benefit) of doing this, is that bringing up the wrong fader can add the comms line to the show audio - and depending on the singing abilities of the crew, can be a good (or in most cases) a bad thing! Handy during rehearsals, when the director, if cans enabled, can bellow at everyone.

 

That's actually what they want to do as they have a 3 minute change where they want the DSM, Lx and Sound Cues to be heard on the PA and the venue we are in doesn't really have stage boxes near the areas needed.

 

Thanks for the advice so far think I will try the 4pol XLR to 3pin one and connect it via a DI so it will not be as affected, And only connect it either a beltpack and nbot direct to the line as I know that will be good bye sound desk ** laughs out loud **.

[dbuckley]

To grab the Tecpro audio just make up a cable, XLR to jack, and solder a 0.1uF cap in the XLR to pin 3, and take the tip of the jack to the other side of the cap, and ping 1 to sleeve. Plug jack into DI box, job done.

[peternewman]

An even simpler solution, which I've used successfully before, with thanks to Rob Kettridge.

The standard for 3 pin comms wiring is:-

 

1: Ground

2: 24V DC

3: Audio

 

So you need to lift the power pin and then swap the audio to pin 2 and ground pin 3 on the connector that connects to the mixer or whatever you're plugging into. Obviously don't ground the 24V supply :) Only problem with this is that the call signal ramps 24V DC onto the signal line which some mixers seem to be able to cope with and reject and some can't. We've got some little canford self powered monitor speakers, little 3" things, that we often use as a loudspeaker station for the comms using exactly this technique and when you press the signal button the cone moves out to it's extent until the signal is released :blink: hasn't done it any harm yet though. I tried putting a cap in series with it to filter off the DC but the ramp up still gets though and it just supplies power to the signal lights so they all slowly ramp on and off rather than flashing :o oops.

PN

[Tomo]

Alternatively, where is the Tecpro base station/power supply?

 

Most models of this have audio in and out jacks or XLRs, so these can be DIed (if necessary) and fed directly into/out of the sound desk as required.

[mackerr]

Here is a link to a page of intercom adapters from Pete Erskine of Best Audio. Most of them are for RTS comms, but can be Clear Com or Techpro by just using channel B. There is a lot of info about high end comms there as well. The page with the comm instructions from Torino is kind of cute, but worth a look.

 

Mac

[henny]

just to add a twist to this,

 

the XLR in on a trantec in-ear transmiter dosent seem bothered about being conected direct to the coms line,

 

odd I know but ,

 

this was found by axadent when I asked some one to linlk the TX to the coms and conected to the coms circuit and not vire the beltpack/adaptor methord mentioned above, I found what he had done a week later on the out.

 

 

I now reguley put the tx on the end of the coms line.

 

this allows wireless coms listening and using Sen EV Rx's feeding of coms to small monitor speakers within the range of the rf , or the desk

[mackerr]

just to add a twist to this,

 

the XLR in on a trantec in-ear transmiter dosent seem bothered about being conected direct to the coms line,

It is pretty common for RF transmitters that will be used as IFB in broadcast situations to be designed to have a comm line as the audio source.

 

Mac