60 foot HDMI run with Monoprice RedMere cable picking up noise? - AVS Forum
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post #1 of 8 Old 01-18-2013, 11:55 AM - Thread Starter
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My set up. Oppo 103, Marantz AV 7005 pre amp, Epson 5020. Just finihsed installing my new BD player, pre and PJ. Did a dry run with 60 foot Monoprice HDMI RedMere cable. Everything perfect, picture, sound etc. Passed a 3D signal through the Marantz 7005 without a hitch. No buzzing or noise in the speakers.

I now run the 60 foot HDMI cable around the unfinished side of the room, lots of 120 volt lines, houses main ground wire. Really have no choice how it has to run as the 60 foot cable just makes it by inches. It is right next to the 120 volt lines, can't avoid it. Hook everything back up and I have a bad buzz/hum from my speakers, running 5.2 set up.

Picture seems perfect. I did go through a bad ground loop hum a few weeks ago which was fixed by a Jennson transformer product in the coax line. Cost $60.00 but worth it. Took the noise right out the speakers, amazing.

I was not interested in the wireless PJ. My first PJ a Panasonic worked with a Blue Jeans 75 foot cable for years but would not pass the 3D signal of the new Epson. This was some fat cable hah. I was hoping I would not have to change it but....Works with 2D, no 3D signal. Cable is 5 years old. If I unplug the HDMI from the PJ, noise goes right away and noise was not there when I had it not the floor for the dry run.

Mono says ferrite might help? Just wondering if they make something else that will shield the cable. Can I sheild the cable myself? Aluminum tape? Just looking for some suggestions as I can't run the cable any other way.

Thanks for the help.

Brian

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post #2 of 8 Old 01-18-2013, 12:08 PM
 
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Assuming you are talking about the Redmere HDMI cable, that can't add noise as you describe to your system. Let me explain...

A group loop hum on a speaker would be 60Hz audio. That happens when the AC frequencies bleed into the audio. Other hum frequencies have similar beginnings.

The HDMI signal does not contain any analog audio. It is only digital. So, for the power line to cause an audible hum in the HDMI line, the AC interference would have to find the part of the HDMI bitstream that had the audio information, convert itself to digital, sum the newly created digital information with the bits that were already there, modify the encoding scheme so HDCP would pass and then repeat the process continuously. Obviously, this isn't going to happen and random bit errors do not produce a continuous hum (or even a hum).

However, I can give you a possible explanation. It is possible that by connecting up the HDMI cable, you've re-created a ground loop particularly if the ground is not the same where the Epson is plugged in versus the Marantz. To see if this is true, run a long AC cord from the Epson and plug it into the same AC socket as the Marantz. If the hum disappears then that is a likely explaination. Unfortunately, that would also mean that any HDMI cable would do the same thing.

A second possibility is that your speaker wire is now close to an AC transformer of some type and that is feeding back into the Marantz.

See what happens if you now remove the transformer that you just added. Unfortunately, these ground loops turn into science fair projects very quickly since they are hard to pin-down.
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post #3 of 8 Old 01-18-2013, 12:10 PM
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Yep, sounds like the ground loop is back. Nothing you can do to the cable will help that. You have to break the loop.
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post #4 of 8 Old 01-18-2013, 01:11 PM - Thread Starter
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Thanks for the help guys. I went through hell to find the buzz/hum the frist time as I did not think it was my cable box. After some research I pulled the coax out of the cable box and the hum went away. Installed the isolation transformer and no more hum/buzz. Ran the 60 foot HDMI RedMere cable accross the floor, this was before the Jennson was installed. . I had assumed the hum would be gone now but it is back. Pull the HDMI off my PJ and hum is gone. Never even thought that the HDMI could not pick up noise. I will try what you have suggested and run the PJ 120 volt line to my power center. Then I will try to remove the Jennson.

Let me ask this, why remove the Jennson? Thanks for the help.

Brian

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post #5 of 8 Old 01-18-2013, 02:01 PM
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If it is a ground loop, one way to break the loop would be to use a fibre optic HDMI cable. But they are pricey.
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post #6 of 8 Old 01-18-2013, 02:25 PM
 
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Quote:
Originally Posted by brianlvi3 View Post

...Let me ask this, why remove the Jennson? Thanks for the help.

Brian

In the event that the Marantz is now picking up the noise from the Jennson. You'll also notice that the Marantz (mostly likely) doesn't have a ground plug. Look at where the AC cable attaches to the Marantz and (I'll bet) you only see two contacts. Its ground is based on what is attached to it.

The AC noise is getting into the receiver somehow and it isn't easy to figure out where.

I might also try disconnecting the speakers and listening on headphones to see if you still get the hum. Then reconnect each speaker one at a time. In the old days, I'd also say to check your phono inputs but that probably isn't even possible now.
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post #7 of 8 Old 01-19-2013, 07:24 AM - Thread Starter
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Hey guys, thanks so much for the help on this. I ran an extension cord over from the PJ to one of my power centers which all my equipment is into, no more buzz/hum. Picture is perfect, sound is perfect.

Just wanted to say THANKS!!!!! I will now make it more permanent by extending the same electric line over to the PJ or making an extension cord out of SJ cord.

Thanks!!!!

Brian

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post #8 of 8 Old 01-19-2013, 06:00 PM
 
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That's great to hear! Glad we could help.
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