Crackling on Com

[corvid43]

The last few weeks we have been getting very intermittent crackling on our show-run channel of com. When it really gets going, it seems to garble the sound of the calling SM. Lately it seems to be getting worse and more bothersome to the crew on headset during the show. But when I try to troubleshoot it, of course I can't get it to happen.

We have an SB-704 for the SM. On the channel in question we have ~10 RS-603 beltpacks, various headset types (mostly PH-88's and Sennheiser HMD25/26's), and a BTR-800 running 3 TR-800 wireless packs. This channel is also fed into 2 KB-702 wall speakers.

I haven't been able to tie it to any specific station/pack or interference. It really does seem to be random, although I mostly have to rely on feedback from the SM's as to when it happens. I thought it could be the wireless, but I still heard crackling when all of the packs were turned off (though BTR base station remained on). I don't know where to go from here, short of ripping apart the whole system and putting it back together, which with so few dark days, isn't a possibility.

I oversee the sound department in a smallish theater and com is my achilles heel, as I come from more of a music studio background....It is driving me mad! Please help!

Thank you in advance.

 

[afreeradical]

Chech the ribbon connector in the base station. I'm assuming it's a Clear Com base station.
And if hearing it in all headsets, chances are its coming from something sending signal not recieving.
And crackle rather than buzz usually reflects something mechanical. Look for something moving.
Dirty pots are also a cause for crackle

 

[corvid43]

Chech the ribbon connector in the base station. I'm assuming it's a Clear Com base station.
And if hearing it in all headsets, chances are its coming from something sending signal not recieving.
And crackle rather than buzz usually reflects something mechanical. Look for something moving.
Dirty pots are also a cause for crackle

Thanks for replying! Yes, it's a Clearcom SB-704...though I don't see a ribbon cable on it.

I agree with your theory that it's something sending. Maybe it's worth it to power it all down and then exercise all of the knobs and connections, using contact cleaner where necessary...?

 

[techieman33]

Could be a bad cable as well.

 

[corvid43]

Could be a bad cable as well.

That was my assumption, but how to find it in a party line, which is essentially a loop??

I like it when things are routed through a console...so much easier!

 

[techieman33]

That was my assumption, but how to find it in a party line, which is essentially a loop??

I like it when things are routed through a console...so much easier!

Have someone sit at one com station, and another move through all of the other sets one at a time. That person should be wiggling cables, moving around, etc. Good luck on the hunt.

 

[afreeradical]

Ya sorry I have sketchy internet in my booth at best so couldn't look up the model, but I sit beside audio and he said about ribbon connector because he had same problem.. (it's in the base station)
If your alone I'd start with cleaning the pots....
But if you can get a helper.... what techieman33 wrote would be your next step in finding it.
Canned air threw all your pots and boxes just may make it better enough to get closer to problem...
I'm home for lunch and looked up the manual for your unit....
I think it different than what my audio op thought.... Much newer and larger and anything I've had to set up....
Maybe an audio tech will read this and give you more, better advice

 

[venuetech]

If it is a wireless you can usually get a good idea about which pack it is by watching the base-station pack activity lights.
have someone take a look at the BTR basestation when the crackle happens.

 

[Jay Ashworth]

You said that you had it occur with the wireless packs off, but the receiver/base still on? Does it go away if you turn the base off?

Cause RF noise coming in over a receiver is a good candidate...

 

[venuetech]

I should have pointed out on the BTR basestation for each belt-pack there is a mute switch. if you are not using a beltpack it should be muted so it does not pickup any stray RF.

 

[Chris15]

What frequencies are the BTRs running on?

 

[corvid43]

You said that you had it occur with the wireless packs off, but the receiver/base still on? Does it go away if you turn the base off?

Cause RF noise coming in over a receiver is a good candidate...

Haven't tried that yet...I will finally have some time on Wednesday to do some serious troubleshooting, and will try this out.

The biggest hurdle is that the crackling can be so intermittent, that I can't tell if what I'm doing is making any effect at all.

 

[corvid43]

Have someone sit at one com station, and another move through all of the other sets one at a time. That person should be wiggling cables, moving around, etc. Good luck on the hunt.

I kind of did this on my own already...I would put the headset on of a pack that I was testing and wiggled stuff.

I have heard the crackling when the system is in "neutral" or "standby": not during show run, no mics on, and no w/l packs on...so the system is essentially just powered on. I would just put on a headset and listen and hear it every now and then.

 

[AlexDavila]

This may be a redundant suggestion, but make sure to check all of your cables in the system, and not just at the XLR connections. I don't know how much movement your wired partyline gets, but all it takes is one little nick in one cable to short your entire line of communication. Not a week ago, I came across just that in my university's space, and every time the ASM would walk away with the pack on his belt, the cable would move and the whole system would crackle and ultimately short. It made calling the show a real nightmare! Additionally, if you haven't already, make sure all your cables are strain-relieved, primarily at the wall connection. Finally, in my experience, dirty "pots" generally only affect the user with the dirty "pot," meaning they would be the only one to hear the crackle when they adjust or bump their volume control. Wired clearcom is just a headache waiting to happen... not that wireless is without its faults too.
Best of luck, let us know if you suss it out.

 

[corvid43]

I have been silent because I thought I had solved it! I was slowly taking things out of the loop and I replaced a cable run on one of the wired packs (where I suspected the problem came from) and it went away. Only to return a few days later! I have a bit of time today and a helper so I think I will go through and do a thorough wiggle test. I also plan on trying to see if I can see it coming in over the wireless at the BTR base station, but the problem is so intermittent that I could stare for hours and not see anything...It was mostly silent last night, but the night before it was rampant. It's really starting to get to me...!

I found one other element that I forgot about that I was going to try taking out of the loop...we have a Sennheiser wireless IEM pack that we have set up as a "listen only" backup com pack that gets rarely used. The transmitter stays on 24/7. So the com line for one of the channels goes into an AudioMan ISO Box, then out of that there is a Y that goes to the Sennheiser transmitter and the BTR base station. It dawned on me last night that the noise could be coming from the transmitter, but then I realized that since the setup is "listen only" is that even possible?? I can definitely power it off for a while to see if it does anything.

 

[corvid43]

I also wanted to mention that all of our TR-800's are set to "push-to-transmit".