Northshore Posted August 30, 2005 Share Posted August 30, 2005 I have posted before on an annoying hum I have had in my HT setup and I have finally solved the problem. After disconnecting and reconnecting components, using cheater plugs and generally being discouraged over the situation I ordered the ISO MAX VRD-1FF from Jensen Transformers. I must say that once the package arrived I was wondering what $60 for this tiny piece of equipment would do for my situation. I simply placed the unit inline between the cable feed from the house and cable box and HUM instantly removed. I would highly recommend this piece to anyone that has a cable hum to bring silence back to your system. Quote Link to comment Share on other sites More sharing options...
SCOOTERDOG Posted August 30, 2005 Share Posted August 30, 2005 I have read great things about this little device. Too bad it won't work with satellite systems. Quote Link to comment Share on other sites More sharing options...
chuckears Posted August 30, 2005 Share Posted August 30, 2005 I've had one of these hooked into my system for quite some time as well, and have found it to be indispensible. I don't know what it is about cable systems and HT; even the installers of my digital cable admitted they had never seen\heard this problem to this degree. Quote Link to comment Share on other sites More sharing options...
sunburnwilly Posted August 30, 2005 Share Posted August 30, 2005 In my experience , cable tv is the biggest contributer to system hum . Recently I had a problem with my cable internet and the tech. that came out dissabled my Mondial Magic Box , " ground loop isolater " . At the time , I did have it hooked up before the splitter that ran to my computer and TV , so maybe it was causing problems . Odd , it had been hooked up this way for 3 years w/o a problem . He said that cable internet is very sensitive and can't tollerate such things . So he got the internet stuff working properly , and wouldn't ya know system hum came on like gangbusters . I reinstalled the Magic Box close to my TV and audio system and the hum is gone . Scooter I don't know about your sat. system ; I had Voom until they went out of business back in April , and Never had a hum problem with it ! I would think that the Magic Box would work with it as well . Maybe Not . I am thinking that you got a bad sat. receiver , any chance of that ? Once Again Here It Is . Quote Link to comment Share on other sites More sharing options...
Bill H. Posted August 31, 2005 Share Posted August 31, 2005 NS, I did the same thing - with a part from Parts Express - Glad you solved your trouble. http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=180-075 Quote Link to comment Share on other sites More sharing options...
Guest BobG Posted August 31, 2005 Share Posted August 31, 2005 The magic box from Aragon/Mondial will NOT work for satellite dish systems. The LNB (pickup thingy on the dish) receives its power from the receiver via the "ground" side of the coax. The MAGIC Box (and most other ground loop isolators) effectively "disconnect" the ground side at low frequencies (such as those that cause the ground loop hum), but in doing so, also block the power going to the LNB. So no picture or sound from your satellite dish. The MAGIC Box (capitalized because it's an acronym for Mondial Anetenna Ground Isolator Circuit and it's a patented, distributed capacitance approach) and other products will eliminate the hum from cable TV and Antennas. Not all of these devices are created equal. Some will degrade the TV picture. The whole problem is due to the fact that "ground" is not true Earth Ground. A true Earth Ground when checked with a voltmeter would show zero potential when compared to a ground reference such as a copper rod sunk deep into the earth. So, this being the case, each "ground" in a system is at some different voltage potential to actual Earth Ground. You can measure your system components chassis voltages and compare to a ground stake or to a cold water pipe. It is these differences in voltage potential that causes current flow between components. It flows on the shield side of the interconnects. And since home audio uses two conductor interconnects (versus the 3 wire balanced scheme for pro sound gear) the shield side of the interconnect is part of the audio circuit. Thus the ground loop noise. The way to eliminate the problem is to eliminate extra ground connections. Ideally, a system should have just a single "ground" connection. It could be via a ground wire from your system to a true earth ground stake. It is more frequently from a three prong AC cord connected to the AC wiring in your home and makes use of that ground. Antenna grounds, satellite grounds and cable TV grounds are all excess and they start the flow between the chassis of your system components. Quote Link to comment Share on other sites More sharing options...
Steve_L Posted August 31, 2005 Share Posted August 31, 2005 Nice explanation. Quote Link to comment Share on other sites More sharing options...
SCOOTERDOG Posted August 31, 2005 Share Posted August 31, 2005 Looks like I have discovered my hum problem. It is actually the HD Sat Box. On Saturday I noticed I could no longer get 780p or 1080i just 480p out of it from the HD channels. I spoke with Direct TV technical department and they said it sounds like there is a problem in the component outs and this is why the hum was being produced as well as the resolution problem. They are fed exing a new H10 receiver to me and it should be here tomorrow. If that does not clear the problem then I will have many little cows. But fwiw direct tv is being very good about this. scooter Quote Link to comment Share on other sites More sharing options...
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