Laptop to TV buzzing sound that changes with picture

Wrong impedance, along with a bad cable, is why you are getting the buzzing.

It has nothing to do with impedance.
Possibley due to poor power supply filtering in the display.

There is no magical cable. It is more trial and error. You could order one from monoprice.com that is a heavier wire gauge and shielding, but it may not solve the problem, due to most likely it is a impedance issue.

Please explain how this is due to an "impedance issue"?

If the sound coming out of the laptop's headphone jack is clean when you listen with good headphones, your next good move would be to pick up a $20 Ground Isolator from Radio Shack.

Do this. Get a pair of powered speakers for a computer desktop and connect the laptop to them, to see if you still get the buzzing. If you don't, then it is a impedance issue between the laptop and tv.

...except that a mismatch in impedance will not cause hum or buzz.

If you still get buzz on a headset, while running on battery power with no other connections, then the laptop is at fault.

Okay. If it only happens when you connect the RGA cable, that means that your laptop is not allowing a complete ground connection back to the tv, even if it is on battery power. If it happens with just the sound cable, it is a impedance issue.

Either way, it is still a issue of impedance, otherwise you would not be getting the problem. Cut and dry.

These are all unbalanced connections. If there were no ground connection there'd be no signal.

This has absolutely nothing to do with impedance. Insisting that it does, while refusing to provide any explanation of how or why, is making me think that you're not 'quite right'.

The only thing 'cut and dry' here is that you don't know what the word "impedance" means.

Please search for common impedance coupling. Jensen Transformers have written a few useful papers on it. And no need for insults!

Why don't you explain how an impedance mismatch will cause hum? Gregzoll can't, maybe you can?

Hello. Bit of a long story but please help me. I have recently finished my basement and used a (very thin and cheap) RCA cable to connect a tv in a seperate room of my house from a dual tuner PVR satellite receiver. problem is now that basement is done I am unable to replace my poor quality cable. Now my tv connected to the RCA gives off a very loud buzz noise from my speakers. When I unplug the L/R audio and leave the video connected the buzz stops. When I plug back in... I almost go crazy from this buzz! I have been researching and I think this my help. I also read about "RCA attenuator" to reduce signal due to "over modulation" This is getting complicated to me. please help. Thank you

Darryl

Can you explain in more detail what the connection is? Do you have one video cable and a pair for audio?

What happens if you just leave the center pin on the RCA audio connected and no push them enough in for the outside ground to connect?

yes ok.... it is the composite yellow video and white and red left right audio. When I dont push the connection in all the way the buzzing is actually louder. Some channels are worse than others. I notice movies and normal shows are not so bad, but sports channels like TSN sports center or NHL network it is TERRIBLE!! like when graphics are on... ticker line showing scores... graphics with the colour red are very distinct! like I said before i know my cable is cheap my mistake. I have just never run into this problem before. So in my research I came across RCA attenuator which was described to me to fix the problem suspected to be "over modulation" whatever that is. said something about over modulation of video interfering and bleeding over into my audio lines causing the buzz or humm. I have seen them available to filter or reduce the signal strength from .5db to 6db?? you heard of this? then the "RCA ground loop noise reducer" this is supposed to reduce noise with grounding.... I dunno. I do know it is mainly ment for car audio. But as I watch sportscenter.... depending on colours displayed (mainly reds and white affect most) and graphics the level of the buzz changes. It really seems like some kind of interference in the audio. Does this explain it better?

As a general rule, hums aren't often fixed by precisely matching impedances. Audio as we know today it is not based on impedance matching. In fact it is based on consciously mismatched impedances, those where the source impedance is only a tiny fraction (hopefully less than 1%) of the load impedance.

What Jensen transformers often do for audio is break undesired conductive paths. They address ground loops and ground potential differences. Thing is, if money matters you can get an audibly equal bang for a lot less money with a Radio Shack Ground Isolator or its equivalent.

Yes, I know.


Yes, in fact pro audio did away with this decades ago.


Yes, often referred to as "bridging the load".

I spent $12 on ebay and bought a ground loop isolator and bam!!!! BUZZZZZZZ gone!!!!!!!!! clear as a bell! Thanks!!!!