Problem with FM Transmitter and Speakers

[aloftnfurl]

This year I've added a Mobile Black Box FM transmitter to our show for the benefit of those driving past our display, and now I'm getting a constant low hum thru the speakers that I have out for those walking past the display.

The MBB transmitter is mounted into a powered weatherproof enclosure (an irrigation timer box) that is mounted next to the LOR controllers.

I have a 3.5mm splitter plugged into the audio output of the LOR1602MP3, with the transmitter plugged into one side of the splitter and a set of speakers plugged into the other side of the splitter.

If I remove the splitter from the controller (with both the transmitter and speakers still connect) I still get the hum, but if I unplug the transmitter from the splitter the hum goes away.

My question is if this is just 'one of those things' that I'm going to have to deal with or if there is a better way to connect my transmitter and speakers to my controller?

Thanks!

[HowardShank]

Sounds like a short or crossover in the output. Maybe the FM transmitter isn't grounded properly.

[wmilkie]

probably grounding, in my experience

make sure everything plugged in all the way on both ends, no loose or bad connections.

[-klb-]

Look for an audio ground loop isolator. Radio Shack usually has them. They are most commonly associated with car audio. Put it in the path between the splitter and transmitter. Should clear it right up.

[Nova5]

you will think it a strange device since it only sits in the line between the source and output devices. it makes no other connection, but it works when its a ground loop problem. its a big wart on a cable. If everything you have its headphone jack connection add about 10 bucks to get to and from the RCA connections the GLI will have.

[Mike Manzara]

I found the transformer (wall wart) sent with the transmitter to be the problem with my MBB. When I plug the unit into a USB port on my computer the hum went away. You may have to invest in a better transformer.

[-klb-]

By plugging into the USB of the same computer as the audio, you also greatly reduced the opportunity for a ground loop in the system.

[Mike Manzara]

That may be true but, my entire sytem (show computer, tuner and FM transmitter) are on a power bar that is surge protected and shielded for EMI and RFI so the transmitter does not have any background noise

[boborino]

If your show computer is a laptop, try using a ground lift adapter (3 prong adapter that prevents the ground plug from making contact. Was my problem, and it corrected it.

[Max-Paul]

I know that this is even stranger sounding. But try unplugging the transformer and turning it 180 degrees if the plug allows it. Seems that sometimes the phasing of the power will make a difference.

[aloftnfurl]

Thanks for the suggestions everyone.

I ended up swapping out the patch cable between the transmitter and the splitter and the problem went away. (The one I replaced was one I had used to replace another cable that ended up having a short in one end. SHEESH!)

I appreciate the help!

aloftnfurl