Cans/Desk Feed

[DSA]

Hi,

 

I have just repaired the bust PSU for the cans - so were back on air, as it were - however I just wondered if the following were possible...

 

Can a feed from the sound desk be put over the intercom?? This would be useful as you could hear the show with it on, and direct say music to the followspotters, when theyre bored!!!

 

But seriously, I was thinking about it, and they do not carry 'XLR' signals do they, even though they use XLR connectors, so is it possible??

 

Thanks,

David

[gareth]

It depends what you're driving the cans with.

 

The more basic PSUs (like this one) for ring intercoms do just that - provide the power, and nothing else. If, however, you're driving your RI with a master base station like this one, you have a 3-pin XLR input on the back (unbalanced, unless you've fitted the mod) into which you can stuff anything you like - a show relay feed, the audio for the football match that you've piped through to the prompt desk monitor, etc. - and mix it into the cans with the level control on the front panel.

 

And the follow-spotters shouldn't be bored, they should be paying close attention to the show and watching for their next pick-up ... :)

[IanG]

You can also insert audio into comms using a headset breakout cable plugged into a beltpack. (ie. XLR to 2x Jacks/whatever). Be careful to attenuate the signal to mic levels though.

 

I use this the other way round to put comms onto the aux busses of the mixer.

[DSA]

No its definately a 'more basic' one.

 

...and about 10 years old at that, but still works well...despite fact that if someone puts a headset down, it sends a nasty earsplitting thud through the headphones!!

 

Anyway, I may try to send an aux from the desk to a input.

 

It is definately a ring system.

 

I just thought that it used XLR for ease of use - i.e. one pin for mic, 1 for ears, and one for ground etc. - so wouldnt be compatible for an audio feed...am I right???

 

Is there any cunning cheap way around this - and how do I wire it!

 

Thanks

 

David

 

P.S. The PSU had bust because an internal 'output' fuse had blown - it was 1A (250W). We had run out of those, so I put a 2A (250W) one in - that will be OK won't it?????

[kalmatthew]

I just thought that it used XLR for ease of use - i.e. one pin for mic, 1 for ears, and one for ground etc. - so wouldnt be compatible for an audio feed...am I right???

 

Well, Cans normally uses a multiplexed system, to allow for, mic, headset, power and signall all to be sent through 3 or 4 pins.

 

P.S. The PSU had bust because an internal 'output' fuse had blown - it was 1A (250W).  We had run out of those, so I put a 2A (250W) one in - that will be OK won't it?????

This is a dangerous thing to do because it means that the fuse is not neccerially the weakest link in the circuit, it could also allow the circuit to overheat and cause a fire. So make sure that you replace it with the corect rating of fuse asap.

 

HTH

 

P.S. Appologies for any spelling erros but the speel klunk is broken atm.

[Andrew C]

I just thought that it used XLR for ease of use - i.e. one pin for mic, 1 for ears, and one for ground etc. - so wouldnt be compatible for an audio feed...am I right???

 

<SNIP>

 

P.S. The PSU had bust because an internal 'output' fuse had blown - it was 1A (250W).  We had run out of those, so I put a 2A (250W) one in - that will be OK won't it?????

If it's a Techpro or similar one core is audio, one core is power and the screen is both screen and power ground. It is quite easy to inject an unbalanced signal. See this page for circuits etc.

 

The fuse? Don't panic, but change it soon! Also consider why it blew. Had you shorted the outputs or is there a fault in one of your beltpacks?

[DSA]

I think someone connected the two outputs together (there are 2 outputs on the PSU). I presume that is why it went phut.

 

Otherwise I dont know - if it happens again I will consider something else...better get a fuse now then

 

David

[Djbarryblue]

Yoy get cans system base stations with aux inputs for doing things like this. They are also handy as we have used them in the past with two way radios so that you can get the two way signal down the cans but you cant reply unless you have a radio. Dont know what the cost of them is ? but if you get it sussed get some Billy connly or Roy chubbs piped down to your follow ops that should cheer them up ** laughs out loud **! :D

[themadhippy]

if its a standard 3 wire system tecpro do a 3 to 4 wire convert,allows you to feed a signal in and out of the comms system,they also do a walkie talkie adaptor that fits the motorola walkie talkies.

[James]

if its a standard 3 wire system tecpro do a 3 to 4 wire convert,

 

I was just about to recomend this, I've used it and find it VERY useful,

 

It has the other benefit of being able to easily pull the cans feed out of the loop - which I have been known to use if someone on cans needs to address the whole cast. in rehersals (And makes making the blackmail tapes so easy......... )*

 

James

 

* Not that I would ever advocate making un-authorised recordings of anyone without their prior permission....

[IanG]

If it's a Techpro or similar one core is audio, one core is power and the screen is both screen and power ground.

Not quite - the audio connection has +12VDC (IIRC) superimposed on it when the signal button is pressed, which you don't want going into audio equipment. You can probably remove this fairly easily though.

 

The pinout on the cans connector is

1: Mic earth/scr

2: Mic signal

3: Earphones earth/scr

4: Earphones signal

 

With a bit of attenuation you can usually use this to inject/receive comms from the line. Ties up a beltpack though, although if your input/output is high impedance you should be able to get away with adding a passthru connector and putting a set of cans on the same beltpack.

[Andrew C]

Did you look a the info on the "DMX512" page?

 

The output to the comms line is protected from dc by a 1uF capacitor, and the whole lot goes in circuit in the same way a beltpack does.

[DSA]

Hang on,

 

All the connections on our system have 3 pin XLR plugs/sockets - so I dont know where this mystery 4th pin comes from!! I presume this is a different setup.

 

I think I'll take it that this is not posssible on our old system!

 

Thanks,

David

 

P.S. Is there any way of:

 

a) making them not always on!

b) cutting out the hum on the circuit?

[Andrew C]

What about the headset to beltpack connection?

 

You can add a switch to short out the mic capsule. Perhaps a push-to-break so that the user presses when he/she wants to talk. Or you could put a tilt-switch in the headset, so it switches off as soon as it's put down.

 

The hum could be caused by poor screening, a loose earth or perhaps a poorly designed PSU.

 

Are you using a proprietary system (if so, which) or a home made one?

[DSA]

No, all connections are 3 pin XLR - each headset plugs into an ICOM socket in the venue - one of the PSUs ring output (3 pin XLR) sockets also plugs into an ICOM socket to power the circuit, if you see what I mean.

 

It is definately not hand-made - however it is quite old - I think it said '93, when I opened the box to change the fuse.

 

It also had lots of bits mentioning BT in it...

 

The main part was an 'uninterrupted power supply' in the middle.

 

David