Did I accidently create a wireless monitor? Please help...

[Pauly]

So,

Long story short, the janitors came in and did a "deep clean" in our theatre and in the process unplugged everything from our soundboard. The show isn't for another couple of months, so while frustrating, it's fixable; however, we have a talent show rental and I needed to get a quick and dirty set up. Here's what happened...

I was getting our monitors back up, and midway through the process I started getting a full signal out of one of my monitors...but it is in no way connected to the board. All that's plugged in is the power cord and a 1/4in. connected to the output that isn't plugged into anything on the other end (just lying on the ground). I'm used to getting a super distorted signal from badly shielded cords, but this was a full and decent sounding signal, the only issue was a very very slight hiss when I turned the music off.

The only thing I can think of is that the installers used the cheapest cable known to man and that somehow it's getting picked up.

I've checked, they're not wireless in any way, and it's picking up any mics, music, etc., that I plug into the board, responding to volume changes, and overall functioning just like a low end monitor...it's just not plugged into anything

What did I stumble upon, and how do I fix it?

 

[lakota651]

A church I used to help out at from time to time had some poor wiring, and every so often you could hear Radio Disney come through one side of the mains when things where quiet. Another space I worked occasionally picked up a Mexican radio station late at night.

So my guess is; do you utilize some sort of FM transmitter for your hearing assist system?

 

[Pauly]

A church I used to help out at from time to time had some poor wiring, and every so often you could hear Radio Disney come through one side of the mains when things where quiet. Another space I worked occasionally picked up a Mexican radio station late at night.

So my guess is; do you utilize some sort of FM transmitter for your hearing assist system?

No FM transmitter, and I've experienced a similar issue to yours before in a different poorly wired space, but even then it was still a distorted sound or radio station. This is for the most part entirely clear and crisp and only responds to whatever my output is on the soundboard. Essentially, I got my monitor working, but I have no idea how

 

[lakota651]

Have you been able to determine which output of the console it is getting signal from (i.e. aux, mains, matrix, etc)? If you were to pull all other outputs from the back of the desk what happens?

 

[FMEng]

The cable that is only plugged in on one end is acting as an antenna. It is picking up a nearby AM station and circuitry in the console is demodulating it into audio. Finish connecting everything back together and, chances are, it'll work fine if it did before.

 

[StradivariusBone]

I had something similar with a short in a floor box with a mic input causing signal to cross over from a cable shield shorting on a monitor output on the other side of the stage. Worst feedback ever and when it wasn't feeding back, the mic was reproducing the monitor feed. Check your terminations.

 

[TimmyP1955]

Do you have in induction loop assisted listening system? The open cable and speaker could be picking up and rectifying that.