Interesting Ground Loop Problem w/DirecTv HD-DVR - AVS Forum
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post #1 of 4 Old 12-24-2006, 08:23 AM - Thread Starter
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I recently had a new DirecTV KA/KU HD satellite dish installed along with a high def dvr. Everything sounded great and looked great when displayed from my Epson cinema ceiling mounted projector and Yamaha HTR-6090 receiver. A few days later I turned the system on again and this time I was getting a loud annoying humm on my subwoofer. The noise appears when I plug in the hdmi cable or the component video cable. I can understand the hdmi cable since it carries audio also but not the component video cable. The only difference from day 1 and day 2 was that the 4 satellite cables were buried underground but there were no connection changes on the receiver or DVR. The humm does not appear using the same hdmi cable when plugged into my DVD player. The ground loop might possibly be coming in on the satellite cables also. I can't seem to find a Satellite "Ground Loop Isolator" w/"F" connector anywhere on the web. I have only found CATV isolators. If anyone has any ideas they can throw my way I would really appreciate it. There is nothing more annoying in hooking up a dedicated HTR 7.1 system only to have a loud humming noise coming over my Axiom Audio subwoofer.
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post #2 of 4 Old 12-31-2006, 09:31 AM
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I am having a similar problem with my Direct TV HD-DVR and SVS sub. It is definitely coming in through the sheild of the two satillite feeds into the DVR (when I remove them the hum is gone). This confused me at first since the only audio path to my receiver (Denon 3805) was through optical connetions for both the HD-DVR and OPPO DVD player. The video paths to a Sharp LCD and Panasonic Front Projector are HDMI where all the switching and distribution is done external to my receiver. The only RCA connection to the receiver is a composite video out to support on screen displays for receiver set-up...... this was the path where I was getting the noise thru.

The HDMI cable from my HD-DVR was feeding Sharp LCD which was also connected to the monitor out from the receiver. I rationlized the noise was coming to the LCD from the DVR via the HDMI cable and returning to the receiver via the monitor out cable. I removed the monitor cable (with the sattilite connection to the DVR still in place) and the hum disappeared. Since I don't use the OSD very often, I can leave it disconnected for the most part which solves the problem (in a band-aid way) for me.

Like you I searched for an in-line isolation transformer for the satillite side and found none. I'm thinking now that the only way I may be able to solve the problem will be with a line level transformer between my receiver and sub. Let me know if you find a solution that works for you.
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post #3 of 4 Old 01-04-2007, 06:48 PM
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I had a similar ground loop problem with my cable DVR. I couldn't find a suitable cable isolation device so I attacked the problem from the electrical power ground side. I installed a three prong to two prong power adapter (Walmart) to disconnect my system from the electrical power ground. No more annoying hum.

It might be possible to modify the connector on one end of the cable to address the problem. My testing revealed that the signal line did not cause any noise only the cable shield/ground connection was the problem. If one could attach a end on a cable in a way that didn't connect the cable shielding, I believe the ground loop would be eliminated. Maybe cutting through the outer cable insulation and severing the shield would also work.

George
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post #4 of 4 Old 02-13-2007, 01:38 PM - Thread Starter
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My subwoofer was connected via a RG-6 cable with an F-connector on one end and a rca connection on the other end. When I replaced the RG-6 coax with a standard rca cable the loud humming dissappeared. Don't ask me to explain how or why but in my case that is what caused the problem. Sorry I did not reply an earlier than now.
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