Buzz from wireless receiver

2mojo2

Active Member
We are putting together a package of wireless mics and receivers for certain users of our high school stage.
I refuse to hand our "good" bodypacks to kids who are not members of our cast, so this cheaper wireless gear is for the various in-school talent and pageant events we support each year.
We started with a Nady Quad receiver and four wireless lavs.
Trouble began when we tried to add a cheap import dual handheld set-up.
My chief student sound tech reported a loud buzz on both channels.
He thought it was lessened by using one channel at a time, but I think it was just softer because he had one channel vs. two channels of buzz open.
I tested the equipment one evening and got no buzz, just a cheap mic that could be tamed by EQ to get acceptable results.
We tried it again a few days ago and the channels were unusable, steady loud buzz.
The noise remains with -all transmitters off
-gain on the receiver all the way down
-no RF signal showing on the receivers
-new cables
It seems unlikely that we are picking up intermittent RF interference, but I can't easily rule it out.
The fact that the Nady gear, as well as other gear, has worked fine from the same position and power supply makes it unlikely that the problem is a power supply/ground loop issue.
I am uncertain what to do next.
Your suggestions?
 
It could still be caused by a ground loop because the handheld receiver is built differently (or badly) than the others. The fact that other equipment doesn't hum is irrelevant. Make a pair of test cables with pin 1 lifted on the female end. Mark the cable obviously as a "ground lift" so it doesn't get used inadvertently.

The receivers could be poorly shielded and picking up noise from another piece of equipment nearby. Power down other close-by devices, one by one, and see if the noise changes or goes away. If you find the interaction, it might be as simple as relocating some equipment.

It could also be defective receivers. The buzz may be internally generated by a circuit oscillation. Just because it is new doesn't mean it works right. Also experiment with phantom power turned off. It could be that the receivers don't have proper DC blocking on the output stage.
 
I'm running sound right now and the sax player swears by him Samson wireless. Not only does it make the sax sound like a kazoo, it apparently also comes with killer bees. There's no electrical ground to lift. I don't have a cable with me to lift the audio ground and I'm not about to go chopping up a cable. The band is loud enough to cover it up, plus a little bit of corrective eq. Sometimes you just gotta cut your losses... If you figure it out post back, I'd be curious to know the fix (other than a pin 1 disconnect).
 
I have removed the equipment from the theater and tested in another radio environment.
The results are pretty much the same.
I conclude that the receiver unit is defective.
I will contact the seller and hope for better.
Matt
 

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