Headset/ClearCom trouble

[Kastle]

I searched through previous topics and couldn't find one that matched my need, so I created one.

The space I'm working in has an old-ish wired ClearCom system (I'm not sure on exact numbers).  Recently, while the box has been turned on, I've been getting a feedback-type noise that my director describes as a "Chewbacca" noise. We've tried different channels, different wires, different headsets, and a different box.  Has anyone else every had this problem? And if so, what did you do to fix it?

[anole]

We just had to troubleshoot our old ClearCom system too.

Do you hear the noise in only one headset or in all the headsets?
If only one headset, do you hear it all the time or only when you're talking through that headset?

[Kastle]

It varies- sometimes it's in one headset, other times it's in all.  When it is in just the one headset, it happens randomly, even when the talk button isn't being held.

[BayAreaSM]

Granted, you're not on wireless (where this happens most often), but have you done a cellphone check?

My LD was on a wired clear com during tech, and had his iPhone 3 (not 3G or 4) next to his comm box, and it would cause our feedback issues. Granted, it happens the most with the wireless coms and people carrying their phones in their back pockets - but this did happen to me with a wired com.

Worth a shot to ask "turn your cell phones off - not on vibrate, but OFF."

[Mac Calder]

Comms loops are very susceptible to electromagnetic interference. Common causes are comms lines running beside power lines, mobile phones near comms lines, microwaves near comms lines... Basically, if people are worried about it causing cancer, there is a good chance that it will interfere with comms.

Also... Are you using light weight headsets?

Light weight headsets with the volume turned up too high will feed back.

They are a bit of a black art

[Kastle]

We've done a cell check in rehearsals- I've had people go as far as putting their off cell phones in a box in the directors office, and there really wasn't much change. The headsets aren't light weight, but we have tried turning down the volume, and it didn't really help.

Other interference is possible, though it really doesn't sound like the typical noise that you get from cell interference.  Is there anything we can do to minimize the noise?

[anole]

Have you checked the connectors in the back to see if they're loose?

One issue we had was the male connectors in the back of the boxes would get loose- you wouldn't necessarily notice just plugging the cables in, but if you unplugged them and lightly pushed or pulled on the prongs they'd move forwards or backwards in the casing easily. This would wind up stressing then breaking connections inside the box, and sometimes it was accompanied by a loose screw rattling around in the box causing random problems.

Have you tried swapping out the order of the boxes to see if that changes anything?

[loebtmc]

do your boxes have batteries? The clearcom systems used at one theater gets nasty and static-y whenever the batteries start to go.

[Kastle]

We've checked the connectors, they're fine. We've tried trading out boxes. (The boxes do not run on batteries.)

It's all just really frustrating.  It seems like we've ran through almost every troubleshooting topic we can, and yet we're still getting this horrible feedback.

[theatregeek89]

Does there happen to be any metal near your comms? We tend to get a lot of feed back when one of the crew touches any kind of metal it causes interference.

[kiwitechgirl]

This might sound stupid, but sometimes if there's something "noisy" plugged into the same ring main as the comms master station, that could affect it.  If you can get hold of an isolating transformer, try plugging the master station into the power through that and see if it makes a difference.  Long shot, but I've known it to work...

[Kastle]

There is a lot of metal.  Unfortunately, I'm right by the dimmer rack.  That could be a problem.

Thanks for your input, everyone!

[PSMKay]

Can you make sure nobody has accidentally created electromagnets in the process of running cable?

[kmc307]

Are you using shielded cables?  Do you have a ground fault somewhere?  Maybe a poor/broken termination on a cable or wall panel somewhere in the building.

Is it possible to get your audio team involved in this?  While many of them lament that comms fall into their department, most of the time they are the most well-equipped to isolate and remove these types of faults. 

[Kastle]

Unfortunately, I'm working with a college/community theatre, and in our space we don't have an audio team.  All tech problems fall to myself, the tech director (who is great, but only on his second show with us), and the director, who is also great but doesn't have a strong grasp on sound/audio stuff. 

The cables seem to be the only explanation left; since that's the one thing that we can't entirely check (they're in the ceiling, it would be a bear to get up to change all of them.) I'm in the process of begging for a new system. 

Once again, thanks for all the input.