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TV appears to be causing ground loop

N

nihilionzero

Member
Hello,
I have a Samsung plasma TV, which is only connected to my APC power strip/conditioner for power and my Marantz NR-1604 AVR via HDMI. The Marantz is connected to an external preamp via preouts, which is going through an Emotiva poweramp.

After disconnecting/unplugging each of these devices, simplifying the system, I've discovered that the only way I can make the buzzing stop is to unplug the TV. All are plugged in on the same circuit. Since the TV is connected via HDMI, there doesn't appear to be any kind of isolation transformer-based fix.

Since the TV power plug is 3 pronged, one solution could be a cheater plug, wherein I use put a cheater plug between the TV power plug and the power strip. Would this be safe? What are the risks?

Are you are aware of any alternative solutions?

Thanks in advance.
Nick
 
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My Panasonic plasma caused an oscillating transformer hum in my Adcom amps that I couldn't get rid of and I tried everything. I finally bought a Humdinger from Audio by Van Alstine and it got rid of the hum completely. It goes between the wall socket and the amps and filters the circuit. It has two power outlets. Money well spent IMHO.
Regards, Sam
 
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Or, before spending anything on parts, if actually connected to CATV or sat or antenna be sure the incoming feed is properly bonded to the household grounding system.

CATV feed is notorious for not being properly bonded.
 
whoaru99 said:
Or, before spending anything on parts, if actually connected to CATV or sat or antenna be sure the incoming feed is properly bonded to the household grounding system.

CATV feed is notorious for not being properly bonded.
Click to expand...
Hmm.. I don't have an antenna or cable. Only thing connected to TV is power and HDMI from Marantz has several devices connected, but it still hums even if I unplug the Marantz.
 
first try unplugging apc and try on battery power . then try tv direct in mains ..if still bad check house power supply .. just had same thing lately but without apc . i do have battery back up though but never thought to try on batteries . turned out to be a live ground . pretty bad situation . not saying you will find similar but worth checking all the same .
 
Several years ago, I experienced an issue with hum in my main stereo system after adding an old LaserDisc player to the setup. It turned out that the hum occurred when the video out of the LaserDisc player was connected to my TV, and when the output of my SoundBlaster USB sound card was connected to one of the inputs on my preamp. My solution at the time was to disconnect the audio output of the LD player from the stereo; if I experience the issue again, I'll try using a 'ground loop eliminator' cable I bought from RadioShack in the years since.
-Adam
 
Clearly, it is the plasma TV. How old is it? If its getting on 5+ years old _and_ it has seen a lot of hours of use, I'd consider rotating it out. The problem is that it is throwing noise out on to the grounding system. Even if you use an outboard surge protector or battery backup system, I'm willing to bet the noise will remain. I'd also conjecture that there are caps that are being run too close to their tolerances and will likely fail soon.

I've got that problem right now with a 42" LED that's just died after I diagnosed it throwing all sorts of messy, spurious signals onto the AC line. It really messed up my ham radio reception, too.

Cheers,

David
 
dshoaf said:
Clearly, it is the plasma TV. How old is it? If its getting on 5+ years old _and_ it has seen a lot of hours of use, I'd consider rotating it out. The problem is that it is throwing noise out on to the grounding system. Even if you use an outboard surge protector or battery backup system, I'm willing to bet the noise will remain. I'd also conjecture that there are caps that are being run too close to their tolerances and will likely fail soon.

I've got that problem right now with a 42" LED that's just died after I diagnosed it throwing all sorts of messy, spurious signals onto the AC line. It really messed up my ham radio reception, too.

Cheers,

David
Click to expand...
Thanks for the response, David. I really hope that isn't the problem because I love my plasma TV and don't really want to replace it. However it got me thinking that maybe it isn't a ground loop. I mean, I thought it was--and indeed there may have been at some point, given that I've been changing equipment in and out--but now I can't find one. I attached a screenshot of a frequency analyzer on my phone. With the current setup, I don't see evidence of a ground loop. Rather, it does indeed appear that my plasma is throwing out some noise on the circuit. So I tried running some extensions into the next room to get the TV on a different circuit. When I did that, there was definitely a clear 60hz signal. Do you think some kind of isolation transformer would help? What's nuts is that none of this was a problem until I added a stereo preamp between my AVR and the L/R speakers.
 

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nihilionzero said:
What's nuts is that none of this was a problem until I added a stereo preamp between my AVR and the L/R speakers
Click to expand...
so if you take the preamp out right now and leave the rest connected ... the hum goes away?

if so

i would first try changing the rca cables on the pre
second try a ground wire from the pre to a ground on the amp
 
orsen said:
so if you take the preamp out right now and leave the rest connected ... the hum goes away?

if so

i would first try changing the rca cables on the pre
second try a ground wire from the pre to a ground on the amp
Click to expand...
Hi Orsen,
Thanks for the reply. I just tested this by restoring to the default state of my system. AVR preouts>poweramp>speakers. There is no buzzing. It sounds as good as it always has. So I guess it's good because it means my TV isn't dying or that I broke it somehow by attempting to use a cheater plug. Though now I'm back to square zero...better than square minus a good TV.

So what should I do now? Everything is on the same circuit (all outlets in my living room are on the same circuit, and they're all on the same power strip anyway).
 
put the pre back
use different rca cables
try running a separate ground wire from the pre to the power amp or avr
 
orsen said:
put the pre back
use different rca cables
try running a separate ground wire from the pre to the power amp or avr
Click to expand...
Thanks for the tip. Per your suggestion I've tried this. Put pre back with different RCA cables from AVR. So three interesting things happened.
1. The buzzing is louder.
2. I took a copper wire an touched it to a screw on the pre and a screw on an amp, and also the AVR. The buzzing got slightly quieter, but was still quite noticeable.
3. As I connect/disconnect the AVR to/from the pre, there is a brief moment where the buzzing diminishes dramatically. If I'm holding the RCA cables (connected to the AVR) about 2-3 inches away from the RCA ports on the pre the buzzing almost diminishes to acceptable levels.

So what can you make of this?
 
orsen said:
try running a separate ground wire from the pre to the power amp or avr
Click to expand...

Might add another loop (assuming that the problem is actually a ground loop).

That would appear to be confirmed by the 3 things nihilionzero did.
Question now becomes where and which piece or equipment is allowing multiple paths to ground on another piece of equipment.
 
woodj said:
Might add another loop (assuming that the problem is actually a ground loop).

That would appear to be confirmed by the 3 things nihilionzero did.
Question now becomes where and which piece or equipment is allowing multiple paths to ground on another piece of equipment.
Click to expand...
What do you mean "add another loop"? You mean attach more ground wires between devices?
 
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