Clicking on snake

[headcrab]

I was running sound across our gym today as we set up for a dance, and I noticed a clicking from the speakers. The computer we use is feeding into a sound board which gives a balanced output, and it went across into another board which then converted into unbalanced for the amp. We have to use extra mixers instead of DI's which we don't have.
But what could be the source of the clicking? When I reduced the output of the unbalancing mixer to 0, the clicking went away, and when I unplugged the snake from the sending board, the clicking continued. When I gated the computer's output on the board, it didn't stop either.

 

[Footer]

Define clicking? Was it this?
freesound :: view sample :: Cell phone interference.mp3

 

[cutlunch]

If you had the computer soundard to the ubalancing mixer disconnected and the clicking continued it may be the mixer.

Have you tried powering the unbalanced mixer and amplifier from a different power circuit then what you are currently using to see if the click goes away. Does the mixer / speakers make this clicking noise when you use them in other parts of the school?

Are there things with motors on the same power circuit such as ventilation / heating fans nearby on the same power circuit?

You said with the mixer when you turn it down the output to 0 the clicking stops.
Have tried turning up each channel on the mixer while they output is up and see if the clicking is on each channel or only one? If the clicking occurs on each channel then it could a problem in the mixers main mix and might be needing a service.

But I would try it out on different power circuits first.
If you have one of those surge protectors / filters plug boards they sell for computers hook the mixer amplfier through one and see if the click goes away.

So the main thing is to do tests to work if the mixer has the same problem anywhere in the school - indicates faulty mixer.
Or does this problem only occur at this point in the gym - indicated inducted noise probably via power supply.

Let us know what you find.

 

[headcrab]

I'm going to guess interference induced by the power supply because everything works just fine when it's all on the same side of the gym, on the same circuit.

 

[museav]

So the clicking is still there with nothing connected to the "unbalancing mixer" but goes away when that mixer's master fader is turned down? Does it seem related to any specific channels on that mixer? Do you hear it on headphones or on any other outputs? Does it vary as you change mute or adjust the level for the channel(s) from the remote mixer?

I'm not sure I understand the comment about using mixers instead of DIs as these are two very different things. I'm also unclear on the "unbalancing mixer", are you saying that you have an amp with only unbalanced inputs and to keep from running unbalanced all the way across the gym you run balanced and then run through a mixer with an unbalanced output? What are the amp and mixers?

 

[BillESC]

Was the clicking on one second intervals? Does you facility have large analog clocks installed?

 

[TimmyP1955]

It sounds as thought mixer 2 is the culprit.

Why are you using two mixers?

Please explain the signal chain in detail.

 

[headcrab]

Indeed.
I was trying to play the music from a computer on one side of our gym to the amp and speakers on the other side. I built a snake out of lots of scrap CAT5e with TRS plugs at each end. Theoretically I could send four channels, balanced, because I didn't connect the ground but used each physical pair to carry the hot and cold of each channel. Each time I tested it, the assembly seemed to work perfectly, but for the fact that the amp doesn't appear to accept balanced signals through the 1/4" input, so I fed the balanced signal from the snake into a small mixer to convert the signal to unbalanced and thence into the amp.
At the other end I connected the snake to a slightly larger mixer, in order that the unbalanced signal from the computer could be sent across the snake as a balanced signal.
My statement regarding the DI's was because I saw that we could have used DI's to convert between balanced and unbalanced except that we don't have any.
The CAT5e I used is not shielded, so it might be picking up RFI.

 

[museav]

DIs do not usually convert balanced line level inputs to unbalanced line level, they typically provide a balanced mic level output. That was what threw me.

Start at one end and work your way to the other with both connections and level settings. By assessing any changes in the clicking, try to determine where it is being introduced. If you unplug the computer output and it goes away or unplug the amp input and it is still there then you've really narrowed down where it is originating. It also might help if you described the clicking.

It is the twisting of the individual pairs in UTP cable combined with a differential input that provides much of the resistance to RFI. Well, it really isn't resistance to RFI, it is any RFI being picked up equally on both conductors and thus being more effectively canceled via the differential input. RFI would also not normally tend to be clicking.