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#29292 - 02/18/04 01:45 PM 770 and fixing the CATV ground loop hum
andyw Offline
Deputy Gunslinger

Registered: 02/18/04
Posts: 2
I received my 770 last week, and after a weekend of listening, I'm very pleased with my purchase. I was using a Denon 4802r (which is now my pre-pro) which has a pretty good amp section, but the improvement with the 770 is quite significant.

My one complaint was that I was getting a pretty bad ground loop hum caused by my cable TV connection--disconnecting the coax from the wall cleared up the problem, but obviously wasn't a long term solution. I had a bit of trouble finding a ground loop isolator (as mentioned in the troubleshooting guide in the 770's manual); the few I found online were on sites I didn't find too trustworthy, and an employee at a local electronics store told me I was crazy to be looking for one...

In any case, Blue Jeans Cable offers a RF Isolation Transformer that fixed the problem for me. Since I had trouble finding one, I thought I'd give them a little free advertising and hopefully help out others who run into this problem.
http://www.bluejeanscable.com/store/rf/rfprices.htm

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#29293 - 02/18/04 04:53 PM Re: 770 and fixing the CATV ground loop hum
ndrayer Offline
Deputy Gunslinger

Registered: 12/17/03
Posts: 5
Loc: Vancouver, BC, Canada
I solved this problem differently:
I had a powerstrip with surgeprotection lying around, and it also has a coax-cable surge protection feature. I use the powerstrip for all the components, put the coax-cable through it and the hum problem disappeared. Therefore, I assume that the coax cable is connected to the mains ground somehow or other within the powerstrip.

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#29294 - 02/19/04 07:19 AM Re: 770 and fixing the CATV ground loop hum
jefny Offline
Gunslinger

Registered: 04/22/01
Posts: 73
Loc: Manhasset, NY, USA
I solved the problem rather cheaply. See my posting below (solving the ground loop hum) by using to inexpensive connectors that converts 75 ohm to 300 ohm and back again. I had both lying around the house.

John

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#29295 - 02/19/04 08:09 PM Re: 770 and fixing the CATV ground loop hum
grundrc Offline
Gunslinger

Registered: 03/14/03
Posts: 66
Loc: Montgomery, TX
I had exactly the same problem. Couldn't get a ground loop isolator from anyone in Houston at the time. I eliminated it by plugging the amp into a seperate surge protector. It worked, even though both surge protectors (the one for the amp and the one for the rest of the equipment) were plugged into the different outlets in the same recepticle. Go figure.

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#29296 - 03/24/05 11:04 PM Re: 770 and fixing the CATV ground loop hum
wingnut4772 Offline
Desperado

Registered: 01/12/05
Posts: 368
Loc: Miami
Voom guy was here today and now - for the first time - my speakers are humming! I unplugged the satellite cable and viola! What is the little Radio Shack Doohickey? Just ask for a connector?
_________________________
My Obsession

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#29297 - 03/25/05 07:13 AM Re: 770 and fixing the CATV ground loop hum
curegeorg Offline
Desperado

Registered: 11/15/03
Posts: 1012
Loc: Raleigh, North Carolina, USA
it is called a "ground-loop isolator"
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This post has been brought to you by curegeorg, thanks for reading.

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#29298 - 03/25/05 09:01 AM Re: 770 and fixing the CATV ground loop hum
wingnut4772 Offline
Desperado

Registered: 01/12/05
Posts: 368
Loc: Miami
I see the ground loop isolator but I thought I saw on these threads somewhere where they sell a little adapter of some sort that you plug the cable feed into and then plug that into thesSatellite. box. I just can't find it. Would that sort of thing accomplish the job and what is it called?
_________________________
My Obsession

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#29299 - 03/25/05 10:22 AM Re: 770 and fixing the CATV ground loop hum
wingnut4772 Offline
Desperado

Registered: 01/12/05
Posts: 368
Loc: Miami
Ok. I fixed it. I just ran the cable through my Monster 2500. I just love the Voom installer shocked
_________________________
My Obsession

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#29300 - 10/19/05 02:30 AM Re: 770 and fixing the CATV ground loop hum
Holydoc Offline
Gunslinger

Registered: 10/02/05
Posts: 20
Andyw,

Thanks for your link to BJ Cables. I ordered the Ground Loop Isolator, and it worked great.


Wingnut,

I have the monster HTS2000. I connected the TV Cable through this bar and most of the humming was eliminated. However if I pressed my ear to the speakers, I could still make out the hum. The Ground Loop Isolator completely eliminated all hum.
_________________________
Holydoc
_ _ _________________ _ _
Onkyo -TX-NR901 Receiver
PolkAudio - RTi12 (Left and Right)
PolkAudio - CSi5 (Center)
PolkAudio - FXi3 (Back and Surround)
SVS - PB-12/Plus (Subwoofer)
Bluejean - Speaker Cables
Outlaw 770 Amp

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