Phantom Mic on clearcom audio

[travislongley]

I am new here and have gotten so many answers from these forums and want to say thanks. I have an odd question. I work at a High School Theatre and have a clearcom system in place(not sure of the base station model right now) I know the belt packs are rs-601's. I have a phantom Mic that hangs above the stage and comes back to the rack straight into a Biamp D60eq 70v amp and then to the two dressing rooms. Somehow we are getting audio from that phantom mic onto the clear com headsets but there is nothing running from the phantom mic onto the back of the base station. My question is it possible to get audio from a 70v system onto the clearcom headsets any other way than the base station? We don't want that phantom mic on our headsets.. it does go away when we turn off the 70v amp but then it also goes away from the dressing rooms where we need it. What is my solution? I hope it is just attached to one of the speakers in the ceiling somewhere because I don't want to crawl around in that space up there a whole lot. Any ideas will help! Thanks!

 

[damjamkato]

Are you sure that there is not a mic on one of the clear-com units that is picking up the sound from dressing room speakers?

 

[travislongley]

Are you sure that there is not a mic on one of the clear-com units that is picking up the sound from dressing room speakers?

Yes I am sure that there is no headset picking it up. Here is a couple pics of my setup attached..

There must be a device that connects to a clear com system and can inject audio from a 70v system into it...

edit:
I don't remember but I think that the remote mic kill actually stops the audio from the phantom mic being on the line, I will test tomorrow and let you know.
One solution I came up with is that since the phantom mic goes to the network signal processor as well as the signal for the House audio, I can combine them into one output and then go to the program input on the Clear-com system and then take the Announce out and go to the bi-amp for the dressing rooms.(That will work as long as I find how the phantom mic is getting onto the clear-com line! And I figure out how to change things on that network processor, I have never touched it..)

 

[Clifford]

The base station is an MS-702. Typically, to get show audio into the intercom system you run a line into the Program Input. Whatever is sent through that will be sent across the whole intercom system. In an older system, it's usually easy to trace where everything connects. The problem with digital systems is that the people building them can do a lot more to obfuscate the signal routing. Once the signal goes into those audio network bridges, they can split, combine, route and otherwise mess with it in ways you can't see. (That said, the intercom system may not run through any of the bridges; it may be a completely separate system. If this is the case, then the problem in somewhere else in the system. You should see where the cabling goes when you get a chance.) Assuming it does run through the audio network bridges:

The other problem is that usually you can't get into these digital systems. They use one of a number of propriety protocols that require various (expensive, licensed) software packages to access and control. In some cases it may even be a violation of the original installation contract to try to change any settings in the bridges or processors. Our new school almost ran into some legal unpleasantness over such an issue.

If the remote mic kill switch stops the audio coming through on the intercom, it sounds like there's just a mic that's left on somewhere near a speaker. Eliminate that before you go around changing the systems. Also, I'd be sure to get permission before I thought about changing anything. I don't know how old your system is, but it may still be under the effects of a warranty or contract. If you go changing things and end up causing a problem, both you and the school could be in trouble.

I also wouldn't advise piggy-backing a dressing room monitor system onto an intercom system. It's not how either were designed to be used, and while it seems technically sound now, you may be getting yourself into a situation later. Since the problem seems to be a loop from the dressing room speakers into the intercom system, I'm assuming there are speaker stations in the dressing rooms. If this is the case, you could get away with simply connecting a split from the mains to the Program Input and turning the volume up on the speaker stations. As long as you don't mind running shows with program audio in your ear, you could get by without using the monitors at all. Many high schools have both speakers and intercom speaker stations in the dressing rooms. At my high school, the amp for the speakers in the dressing rooms also fed the lobby (and the booth, for reasons unknown). Since we had no TVs in the lobby, it seemed odd to have those speakers on, broadcasting show audio during the performance. To get around this we usually just ran program audio through the intercom, with the volume left up on the speaker stations in the dressing rooms.

In short, don't reinvent the wheel, and don't do anything that will get you in trouble or be unsafe (which will usually get you in trouble anyway).

 

[travislongley]

Thanks for your input. I know this building went to the lowest bid. As a result my House speakers are DEAD. My rack has a big green button for power and that turns the whole rack off but it does not control the powered speakers above the front of the stage and being constantly on for 8 years(Age of building) has killed them. I do not have any intercom Panels at ALL, there is just an XLR jack for the intercom in the dressing rooms and I have nothing hooked to it at all. I will look into the contract, but I don't think there is one anymore as all of the Big Wigs at the school district level have told me to find anyone who will replace the speakers to give me a quote for them... I would prefer to run shows with program audio in my ear rather than LOUD Scratchy program audio that is being picked up from a phantom mic that is only about 20ft away from the mains... Gah I will figure something out.

Edit: Could there be a second Main Station on the network that is not powering the headsets(But only powered from the first main station) but is giving program audio from the phantom mic onto the headsets?

 

[Clifford]

It's a school, everything goes to the lowest bidder. Welcome to the world of education system purchasing! Not surprising that they used speakers that aren't rated for being on continuously, but still disappointing. Do you know the brand of the speakers?

The contract still exists, they don't disappear. What changes is if certain parts of the system are still subject to work agreements with the installer, or whether warranties still cover any components or work. At eight years old, you're probably clear; but it's still best to check before you go ahead changing anything.

Are you sure there are no speaker stations anywhere in the system? If there is a concessions/ticket booth, those often have a speaker station instead of a wall jack. These are also the places people usually forget when thinking about an audio system. Think about any other shop, office or green room spaces that may be similarly equipped.

It's extremely unlikely there's another base station on the system. It's possible there's a power supply (PS-702) somewhere, could be white or blue. Check the amp rack to see if there's any equipment there. These types of system they put in schools usually have the simple input racks like you've got in your booth, but the wireless receivers, processors and amps are in another rack somewhere else in the theatre. You can check there to see if there's any other ClearCom equipment, but it's unlikely there's something hiding there that you haven't seen before. If there is a power supply there, those have a program input. There may be something coming from the audio network bridge in the amp rack sending some sort of program audio into that. The only other thing likely to be on the system would be a remote station (RM-702). It looks like the base station you have in the rack in the booth, but could be white or blue. These don't have program input though, so this being the issue is unlikely.

 

[travislongley]

I will have to look for a remote power supply, that may be what it is, It does not kill the signal if I hit remote mic kill from the main station and yes I have thoroughly looked for a speaker station and there is none, not even in the dressing rooms or ticket booth, or in the choir or band room. I will do some looking in cabinets maybe that power supply is hidden because on the main station long lines is not enabled, but I know the end jack is atleast 300ft away from the main station or more... I know if there is another power supply with a program level going into it, the signal is somehow coming off of the dressing room speakers because when I turn off the 70v amp, the signal is gone from the headsets. Somehow you must be able to reduce from 70v to line level...

Edit:
A Quick Google search answers my last question, there could be something to go from 70v to line level XLR. http://www.bhphotovideo.com/c/product/570414-REG/Australian_Monitor_DROP_ME_DropMe_70V_to.html

 

[Chris15]

Yes you can get devices that go from speaker level to mic level
However there is also a possibility that you have the audio being coupled into the comms line.
ie. The comms line and the 70V line run parallel for a long length and there is a magnetic interaction between them.
This will be significantly harder to solve...

 

[travislongley]

Yes you can get devices that go from speaker level to mic level
However there is also a possibility that you have the audio being coupled into the comms line.
ie. The comms line and the 70V line run parallel for a long length and there is a magnetic interaction between them.
This will be significantly harder to solve...

Thanks for this suggestion, I think they do run parallel, probably both to the dressing rooms first. That is an option I will look into if I can't find a secondary power supply. I would have to turn the 70 volt line into a signal line and put the amp in one of the dressing rooms so that there would be no interference..

 

[eqrunner]

Yes you can get devices that go from speaker level to mic level
However there is also a possibility that you have the audio being coupled into the comms line.
ie. The comms line and the 70V line run parallel for a long length and there is a magnetic interaction between them.
This will be significantly harder to solve...

This would be my same suggestion. From the photos, I would take an educated guess that both the com wires and the speaker wires are running out of the rack bundled together. And I can almost guarantee the shielding on the cables going to the speakers are lightly shielded with a thin piece of foil, and not cable shielding.

You can trouble shoot it by pluging in a different source to the amp. (Like a MP3 player) and see if that music is heard in the clear com. (This would prove the phantom mic to amp is not where the interference is occurring.)

How would I solve this? Find a way to add shielding on the Amp to Speaker cables. Or try and isolate the Clear-Com cables separate from the speaker wires.

 

[Chris15]

I cannot remember the last time anyone in the real world used a shielded speaker cable...