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Brijaws
01-27-2005, 09:39 PM
Anyone getting Buzing when integrating Cable Boxes into their house audio systems? I found that its been a ground issue w/ the coax. If we pass the coax through a PANAMAX AC Surge we kill all Buzz and Hums on the lines...

Any other ideas on how to rid this?

mr2channel
01-27-2005, 10:42 PM
a coaxial ground hum isolator is the most common fix, I prefer Jensen transformers over all others I have tried, they seem to reduce the hum the most. www.jensentransformers.com A Bill Whitlock product, this fella wrote the book on ground hum isolation.

AudibleSolutions
01-28-2005, 12:26 AM
Most cable TV hum issues are the result of poor votage blocks on their taps. 2Channel has given some good information but you can complain to the cable company. Out of curiousity, do you see a hum bar on the TV or is it only present on audio? Is there a CATV signal amp in the system? Are the TV and the audio system on the same circuit or are they different?

If you want to minimize grounding issues try to keep all electrical connections you use on the same phase. Not always easy to accomplish but if you can accomplish this it can minimize grounding issues. 2Channels trouble shooting tips elsewhere are very helpful in determining which product or wiring is causing or introducing the ground loop.

Alan

Anonymous
01-28-2005, 07:05 PM
Making the equipment on to same phase is not the solution. Checking and verifying grounding problems in the system is.

Kelly
01-29-2005, 04:51 PM
Making the equipment on to same phase is not the solution. Checking and verifying grounding problems in the system is.

So. Who are you, and how do you know this is so?

Rather amazing that in days past, I've had interconnected systems have a hum which was eliminated by placing the power circuits in phase. That would seem to indicate that having the devices on the same phase IS, sometimes, a possible part of the problem.

Brijaws
01-29-2005, 05:12 PM
Thats a good question for Larry. Is it a netural load balance kinda thing?

AudibleSolutions
01-29-2005, 08:36 PM
The reason you want to keep your circuits on the same phase is that there can be differences betwen ground and phase A and Phase B. Keeping electrical outlets on the same phase removes that factor from any ground problem.

If your problem is the residual voltage form CATV line amplifiers that their taps have not removed ( as they are supposed to ) then the above will not solve the ground problem. A CATV isolation transformer will be required.

If you have interconnected systems, say some equipment in a centalized rack and others decentralized throughout the home then having those systems on the same phase is good practice but not always possible. Often those homes have multiple sub-panels and there can be differences in ground potential between different panels.

There is a difference between good practice to avoid ground problems and trouble shooting the origin of the ground loop once you have one. We do a fair amount of work in apartments where placing the A/V equipment on the same phase is no problem. In medium sized homes it is possible but challanging to acomplish this and in large homes almost impossible. That is why there are isolation transformers and even here some trial and error is required to determine the best place for it. Usually I would argue a video isolation transfromer should be placed as close to the display as possible but there have been times where it had to be placed before it was connected to the matrix switcher.

It is not similar to balancing phases. It occurs because there is a difference in pontential between the two phases and ground ( which is why removing the 3rd prong works to remove the ground loop although doing so removes your insureance liability. )

Alan

Toronto122
02-14-2005, 11:46 AM
I run into this problem all the time...

I know...what kind of schmuck has a re-occuring ground problem..??

Well, here's a solution that works for me.

Take a piece of wire (14g or bigger) and connect it to the shield (ground) of the input coax. Connect the other end to an A/C ground. It gets rid of the noise every time for me.

Have a nice day!