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Hum/Buzz/Static in my ClearCom
Hello, I am stumped with a bit of a problem. The ClearCom system that
is installed at the concert hall I work at has been developing a temper lately. Ever since last year it has had a buzz in it. Well, it's not specifically a buzz, it's a combo of a hum, buzz, and static. Last year, if you were to plug in a belt pack at various ClearCom jacks around the hall, a short would occur and the call light would lock on on every receiver (PS. they are all in series). If you unplugged that pack, then everything would go back to normal. Well, this year, it's my board that is causing the problem. I am using a Mackie SR40-8. Last year my board didn't cause any problems, but I came back in the fall and it was doing it. The only thing that I can think of is to take a multi-meter and go down the series and probe each jack to see when a voltage change occurs. Does that seem like a possible plan or is it a crap plan. I'm honestly shooting in the dark here. Please help me out. -Luther |
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#2
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Luther Bell wrote:
Hello, I am stumped with a bit of a problem. The ClearCom system that is installed at the concert hall I work at has been developing a temper lately. Ever since last year it has had a buzz in it. Well, it's not specifically a buzz, it's a combo of a hum, buzz, and static. Can you break the chain at various points along the line and see when the noise goes away? Last year, if you were to plug in a belt pack at various ClearCom jacks around the hall, a short would occur and the call light would lock on on every receiver (PS. they are all in series). If you unplugged that pack, then everything would go back to normal. That sounds like a badly damaged belt pack. Well, this year, it's my board that is causing the problem. I am using a Mackie SR40-8. Last year my board didn't cause any problems, but I came back in the fall and it was doing it. The only thing that I can think of is to take a multi-meter and go down the series and probe each jack to see when a voltage change occurs. Does that seem like a possible plan or is it a crap plan. I'm honestly shooting in the dark here. Please help me out. What does the Mackie have to do with anything? Tell me you aren't trying to take an audio feed from the clearcom system. I take it you have an installed system where the cabling is permanent and loops through various paralleled XLR connectors around the hall, and you just plug belt packs into the installed cabling? --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
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#3
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Can you break the chain at various points along the line and see when
the noise goes away? I can't break the chain without soldering... What does the Mackie have to do with anything? Tell me you aren't trying to take an audio feed from the clearcom system. The Mackie is just illustrating the point that last year, the beltpacks caused the problem with the call lights, and now this year it's the mixer that is causing the problem...and the Mackie that I am using is designed to have an input of an intercom system... I take it you have an installed system where the cabling is permanent and loops through various paralleled XLR connectors around the hall, and you just plug belt packs into the installed cabling? That is correct -Luther |
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#4
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Luther Bell wrote:
Can you break the chain at various points along the line and see when the noise goes away? I can't break the chain without soldering... What does the Mackie have to do with anything? Tell me you aren't trying to take an audio feed from the clearcom system. The Mackie is just illustrating the point that last year, the beltpacks caused the problem with the call lights, and now this year it's the mixer that is causing the problem...and the Mackie that I am using is designed to have an input of an intercom system... Uh-oh. And there is no transformer isolation on the Mackie, is there? That sounds like a different issue, the fact that you're plugging an intercom with a separate grounding system into a console intercom input that's attached to an audio system with a different grounding system. That might indeed cause a buzz. This sounds to me like it's totally unrelated to your issue of the broken beltpack. I take it you have an installed system where the cabling is permanent and loops through various paralleled XLR connectors around the hall, and you just plug belt packs into the installed cabling? That is correct If you unplug all of the inputs and outputs from the Mackie and plug it into the same outlet that the Clearcom power supply is plugged into, the problem goes away, right? --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
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#5
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Luther Bell wrote: Hello, I am stumped with a bit of a problem. The ClearCom system that is installed at the concert hall I work at has been developing a temper lately. Ever since last year it has had a buzz in it. Well, it's not specifically a buzz, it's a combo of a hum, buzz, and static. Last year, if you were to plug in a belt pack at various ClearCom jacks around the hall, a short would occur and the call light would lock on on every receiver (PS. they are all in series). If you unplugged that pack, then everything would go back to normal. Up to this point, it sounds like you have a damaged belt pack. Once you fixed that pack or stopped using it, did this problem go away? Well, this year, it's my board that is causing the problem. I am using a Mackie SR40-8. Last year my board didn't cause any problems, but I came back in the fall and it was doing it. The only thing that I can think of is to take a multi-meter and go down the series and probe each jack to see when a voltage change occurs. Does that seem like a possible plan or is it a crap plan. I'm honestly shooting in the dark here. Please help me out. -Luther Your board with a clearcom built into it? Or are you somehow feeding intercom audio into your board? Where is the intercom power supply? Sounds like you may be getting a ground loop via the intercom system. Need more data. --Dale |
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#6
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#8
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That clearcom has a telephone 48V power supply?
sounds like either the PSU is getting tired or you have a short between shield and one of the conductors. check with a voltmeter between each conductor and the shield. put a 300ohm resistor between shield and each conductor and see how the voltage sags. "Luther Bell" wrote in message ... how would you suggest that I check for continuity?? (this is all new to me) -Luther "Mike Rivers" wrote in message news:znr1097535242k@trad... In article writes: Hello, I am stumped with a bit of a problem. The ClearCom system that is installed at the concert hall I work at has been developing a temper lately. Ever since last year it has had a buzz in it. It sounds like you might have a short between the shield and a conductor or maybe a broken shield connection somewhere in the signal path. I'd suggest first disconnecting all of the intercom stations and check for continuity and shorts in the intercom cable. If you find a problem, you'll just have to take things apart until you find the short or the break. -- I'm really Mike Rivers ) However, until the spam goes away or Hell freezes over, lots of IP addresses are blocked from this system. If you e-mail me and it bounces, use your secret decoder ring and reach me he double-m-eleven-double-zero at yahoo |
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#9
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#11
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WillStG wrote:
Stuff installed in the wall rarely goes bad Ture, but sometimes things not in conduit are subject to rodent munching. -- ha |
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#12
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In article writes: how would you suggest that I check for continuity?? (this is all new to me) One way is to use a cable tester. Here's about the most complete one you can buy: http://www.ebtechaudio.com/swizzdes.html There are simpler and less expensive ones. The cheaper ones aren't any less reliable, but depend more on your ability to interpret what they tell you. You can also use an ohm meter (the Ohms range or continuity function on a multimeter) by measuring for continuity end-to-end on each conductor of the cable, and by checking for shorts between any two of the three wires. You can check for shorts with nothing connected (and in fact there SHOULD be nothing connected) on the intercom string, but to check for continuity, you'll need to do an end run. The easiest method to understand is to just string a known good cable (or more likely a bunch of cables strung together) from the far end of the intercom chain, for example, the stage, back to the near end, for example the mixing position, and measure continuity through the installed intercom chain and your "extension." The Swizz Army Tester has a test plug that you plug into the "far" end of the cable so you can do all the testing from one end. You can build something like that once you understand continuity measurements. -- I'm really Mike Rivers ) However, until the spam goes away or Hell freezes over, lots of IP addresses are blocked from this system. If you e-mail me and it bounces, use your secret decoder ring and reach me he double-m-eleven-double-zero at yahoo |
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#13
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(hank alrich)
WillStG wrote: Stuff installed in the wall rarely goes bad Ture, but sometimes things not in conduit are subject to rodent munching. Sometimes stuff in conduit too, or at least in the box that the conduit breaks out into ( I had chipmunks nesting in my Central Air Conditioning unit control box, and they had chewed through the thermostat control line! Rodents...) Will Miho NY Music & TV Audio Guy Off the Morning Show! & sleepin' In... / Fox News "The large print giveth and the small print taketh away..." Tom Waits |
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#14
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WillStG wrote:
Sometimes stuff in conduit too, or at least in the box that the conduit breaks out into ( I had chipmunks nesting in my Central Air Conditioning unit control box, and they had chewed through the thermostat control line! Was David Seville holding the screwdriver? |
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#15
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Mike Rivers wrote:
In article writes: Your board with a clearcom built into it? Or are you somehow feeding intercom audio into your board? Some do, though you don't see it very much any more. I didn't realize that the Mackie large format consoles had this feature. -- I'm really Mike Rivers ) However, until the spam goes away or Hell freezes over, lots of IP addresses are blocked from this system. If you e-mail me and it bounces, use your secret decoder ring and reach me he double-m-eleven-double-zero at yahoo According to the pdf manual it does have built-in Clearcom support - never seen that before on an audio mixer/console, a handy thing to have for live sound or permanent installs in theatres/etc... Something important to keep in mind with Clearcom (the garden variety single channel stuff anyway) is that it's unbalanced audio as well as DC signaling on pin 3 and +30v on pin 2. Ground is fortunately still pin 1. When you see a call light flashing it often means that somewhere in the system the wires for pins 2 and 3 are touching (kinked cable, stretched cable at an XLR connector, etc). When you see the call light turn on solid when plugging in a certain cable or beltpack, often means that you have a "reversed polarity" cable. (often refered to as "out of phase" but that's a topic for Google, it's been discussed too many times). As with any system, if it all seems wrong, start with the most basic configuration (i.e. the power supply, one XLR cable , one beltpack/headset) and see if that works properly. Then add ingredients and stir till you find the culprit(s). Good luck Paul |
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