Any A/V specialists here? Ground loop hum.

[Abendage]

Hello everyone,

Just finished installing a Jensen JWM6A DVD/stereo combo in conjunction with a Samsung (12v) 24" LED TV. Anytime the TV is turned on I get a hum, here are the scenarios I've tried and the results starting with hum being loudest to quietest.

1.  TV plugged directly into 12v outlet, HDMI cable connecting TV and stereo, hum very loud.
      a.  Connected TV and stereo to the same power source, literally wire nutted together, no change.
2.  TV plugged into inverter using the 120v 12v adapter, HDMI connecting, still loud, little bit less than 1.
3.  TV plugged into 12v, using RCA cables, hum quieter but still definitely present.
4.  TV plugged into 12v, no connection to stereo, still get a little bit of a hum, but is manageable.

I really don't want to use the inverter as the fan on it is almost as annoying as the hum. It seems the TV just sharing the same 12v power source creates feedback, with no a/v cables running to the stereo. Right now, I think my best bet would be to use RCAs with isolaters to get the hum low, but not gone, but it seems to be a waste to not use HDMI. Any experts here that have any ideas to isolate these things?  This is all on battery, no converter, no shore power.

Thanks!

 

[Bobtop46]

Try this:

https://www.amazon.com/BOSS-Audio-B25N-Ground-Isolator/dp/B000LP4RMG/ref=pd_bxgy_107_img_2?_encoding=UTF8&pd_rd_i=B000LP4RMG&pd_rd_r=JZ5ZAVJT99B4WZSZSZEE&pd_rd_w=LpBwT&pd_rd_wg=BrAfI&psc=1&refRID=JZ5ZAVJT99B4WZSZSZEE

 

[Abendage]

I've thought about that, but it is a video signal that is causing the noise and I've read those don't work on video signals. The stereo is the DVD player, so there is no audio cables between the tv and stereo, just video.

Thanks for the input!

 

[thesameguy]

Are you sure you have a good ground on the stereo itself? If you have any hum on just the stereo, that's where your ground problem is. Honestly, it's a Jensen stereo so the internal construction is inherently suspect. I would try grounding the cage directly to a ground point and see if that gets you anywhere.

 

[Abendage]

I'll check it out, I'll run a jumper directly from the battery to see if it's the stereo ground, but since when the TV is off, all is fine, I think it's an issue with the TV.

Thanks!

 

[Mfreyder]

With only the TV on and running off the battery do you have a hum?

Was there any kind of audio/TV in the coach before and did you have any hum with them?

Reason I asked, I had a battery cause a hum years ago. Was the strangest thing. We ran all the equipment on the bench connected to a converter and it all worked fine. Once installed, we had hum. We turned off everything by removing fuses and flipping breakers to try to find the source of the hum, changed the battery and the hum went away. Was not a ground loop problem. If you have the ground on the stereo connected to the same point as the ground on the TV, there is no loop.

Mike Freyder

 

[John From Detroit]

I have the same problem when I run my computer on 12 volt DC with my ham radio. A total isolation interface is not possible due to the RS-232 connection, but I do have a total isolation interface for the audio links Not unlike the one listed above.. basically it is transormers for audio in and and out (Need better ones) and an Opto-Isolator for the control line (Push to Talk)

Now if I can find an isolator for RS-232 I'll be happy.