Help - Advice requested on buzzing from Cable Box audio feed to AVR

TheAdvocate

Platinum Member
Mar 7, 2005
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I have a Scientific Atlanta 3250HD cable box feeding RCA cables audio / HDMI vid to a Denon AVR 1609. I get HORRIBLE buzzing while watching all cable channels. At first, I thought it was a blown channel in the Denon, as I didnt get this buzzing from my Bluray feed (which is also passing audio along RCA). However, I switched the two and the buzzing continued.

Before I go dropping money to try to replace components, I thought I'd see if anyone else has had this problem.

And yes, my Denon AVR is a tad outdated. But right now isn't the best time to invest in a new unit. If I can beat this issue, I'm happy with the setup for now.

Thanks!
 

Fallen Kell

Diamond Member
Oct 9, 1999
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Is it a high pitch buzz or a low pitch buzz? My guess is a low pitch buzz and that you are dealing with a ground loop problem where the coax cable is not properly grounded, and thus you get a 60Hz buzz from 60Hz cycle time on AC power, as it is grounding over your audio connection to your receiver.

Only ways to fix it are to have the cable company properly ground the coax cable, ground it yourself by connecting through a high frequency grounding block, get a cable box that has a proper ground, or connect your audio over optical S/PDIF from your cable box (and do not connect the HDMI to the receiver, otherwise the ground loop will move to using the HDMI cable).
 

TheAdvocate

Platinum Member
Mar 7, 2005
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It is low pitch.. low and powerful (has some oomph). I have not ever had to ground a coax cable. Do you think the cable company might do it if I put in a service call?

I was going to go the route you suggested with optical, but I have to do video via HDMI, so it sounds like that is out.

Thank you very much for your explanation though. that makes sense.
 

Fallen Kell

Diamond Member
Oct 9, 1999
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Ground coax? Don't bother. Spend $20 at Radio Shack:
http://www.radioshack.com/product/index.jsp?productId=2062214

I think Monoprice may have some now too.

Some boxes also let you run digital audio through optical even with HDMI connected, btw.

Yeah, but that costs more than just properly grounding your coax cable.

Grounding Block: $0.44
http://www.satpro.tv/single-cable-ground-block-high-frequency-3ghz.aspx

HowTo:
http://www.ehow.com/how_7577543_ground-cable-splitter-electrical-ground.html
 

TheAdvocate

Platinum Member
Mar 7, 2005
2,561
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It's coming from my receiver. I don't know why i didnt check before. But i was tapping on my rca cable ttips and getting a microphone type boom. If they touched i got the same feedback i had in my speakers. I am going to try to find some super thick cables.... any suggestions are welcome.
 

nsafreak

Diamond Member
Oct 16, 2001
7,093
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It's coming from my receiver. I don't know why i didnt check before. But i was tapping on my rca cable ttips and getting a microphone type boom. If they touched i got the same feedback i had in my speakers. I am going to try to find some super thick cables.... any suggestions are welcome.

These from monoprice for $3.59 or a bit more if you need more than 6 feet, less if you need less length of course.