75-300-75 Hum Fix Really Degrades My Cable! Alternatives? (1 Viewer)

[Dave Simpson]

Fellas,

I purchased a used Parasound HCA1000 yesterday, had the dreaded hum, which was easily traced to the cable tv, and solved with the 75-->300-->75ohm fix. But the fix has really murdered my cable tv picture. So what now? Before I call the cable company, from whom I don't expect too much cooperation, is there some sort of video signal boosting box (inexpensive) I might look for in Rat Shack, or elsewhere? If it means anything, I'm in the Toronto area, on Roger's Cable. Thanks for any help you may provide.
Cheers.

DS.

 

[Brett Miles]

I have the same problem with the Parasound 1201. Of course, the cable people were pretty much no help on the matter, and I also went with the same fix. There is something better, but it isn't cheap. Something like this or this . I don't know much about these products other than their existence. I deemed it not worth 40% of the price of the amp causing the conflict at this time, but it's still in the back of my mind for later. Try a forum search for these products and you'll probably find some info. This issue comes up fairly frequently. Good luck.

 

[Dan Cabral]

Yeah, I think Brett hit the nail on the head with that first link.
I think you simply need to install a ground loop isolator, which should solve the hum problem.
Here's a fairly quick explanation of a ground loop:
http://www.elect-spec.com/faqgrdl.htm
Here's a cheaper isolator from Polk:
http://shop.polkaudio.com/customer/p...uctid=38&cat=6

 

[Brett Miles]

Whoops, for some reason the second link didn't go where it was supposed to. Click on "magic" and then "magic box" for what I was intending you to see. Btw, sweet find on that Polk isolator. That's more in the range I'm willing to pay. I wonder if it works the same?

 

[Dan Cabral]

I was under the impression that Radio Shack, BB, and 6th Ave. carried ground loop isolators, but I haven't been able to find one any of their websites.

Luckily, I've never needed one, but did run across this problem with a friend and the ground loop isolator fixed his problem. Not sure where he got it.

 

[Mike Matheson]

Some other "eliminators" or isolators are mentioned in this post.

 

[Bruce Chang]

Try breaking off the ground plug on the power wire. I did this with my cd player and tube amp, problem soved.

 

[Chu Gai]

actually i'm a little surprised the picture quality degraded that much. It might be that you're signal strength just isn't adequate. Personally, before I'd start exploring other options, I'd call in the cable company. You may get a repair person who can address the grounding problem in other ways and he'll check on your signal strength.

 

[Wayne_T]

Bruce,

Quote:

Oh yeah, and there is a bonus to fixing ground problems properly rather than floating grounds by breaking or lifting plugs. Your system will sound better.

 

[Todd Hochard]

I agree with Wayne. Noise on the ground indicates a signficant circulating current. This not only adds to noise in your components, but greatly compromises any surge suppression devices you may have. Many of them shunt to ground, which will be ineffective, if there's substantial noise on the ground.

Remember, the ground on EVERY outlet in your house is likely compromised, if there is noise on the ground.

Todd

 

[Lee-c]

It would be great if people could post which of these devices in their experience works the best
without any negative side effects to the cable picture.

Are all of the more expensive devices like the Mondial "magic box", Polk Audio "ISO-MAX" and
Tributaries "ground guard 1" equally good at stopping the hum completely without causing
any cable picture problems?

 

[Dave Simpson]

Hey guys, thanks for all the feed-back! Cheater plugs and/or breaking off the ground prong are not possible remedies I considered for a moment; just not interested in a shocking good time from my gear, is all, but to each, his own. 'sides, cheater plugs are illegal here in Canada.
Solved the problem to my satisfaction today with one of these seen in a post by Marc H. in this thread here . Cost was $20CDN, and the cable tv picture is restored to pretty much its original state prior to the installation of the amp. A great improvement over the 75-300-75 fix. Time to enjoy some swingin' two-channel! Cheers.
DS.

 

[Ken Custodio]

I would recommend getting the cable company to put a new ground on your incoming cable. But if your situation is like mine and a new ground didn't fix the problem and have had unfavorable results with ground loop isolators, I would use a cheaters plug. I know A LOT of people here will say that is a terrible idea but I asked a few knowlegeable electrical engineers at where I work and they all basically said that using a cheaters plug technically is "Less Safe" but unless you are grounded say holding onto a wire that is buried into the ground or standing on a concrete pad there is very little chance the current will want to pass thru you. And if you use a 12V trigger that will further decrease your chances of getting shocked since you will have less contact with your amp. Also, I have noticed that most of my equipment only has two prongs anyway, but I know that an amp is different because it is high current. I am always looking for ways to solve my ground loop hum problem other than using a cheaters plug, but I can't live without cable until I find that solution

 

[Dennis Oblow]

I had good results using the xantec isolator and it is inexpensive with no negative impact on my cable picture

 

[Kevin C Brown]

More than likely, if the cable company put in a new ground, that wouldn't solve the problem. You have to get them to tie their ground to the existing house/apt ground. Otherwise, you can have a potential between the 2 grounds, and bingo, ground loop.

 

[Jeffrey Chin]

i witnessed the exact same problem, except i have comcast digital cable. i have it connected to my replaytv as well. save yourself time and headache by buying one of these babies. problem solved.
3 words:
MONDIAL MAGIC BOX
http://www.audioadvisor.com/store/p...20TV%20Isolator