Hum is gone!

[lanchile07]

Well,I would like to share this weird hum problem with you.
all started two days ago.I have two dish receivers,one of them is connected to my LM3875 integrated amp.well two days ago,We had a big storm (snow) so,I lost signal in my dish and I did not have TV.so I have cable INTERNET service.I splitter the signal one for the modem and the other to my TV,so I got some basic cable channels.so far so good.well after the storm passed,I kept the splitter and the cable connected to my TV since I am using "S-video" input it will not affect anything,if there is an storm in the future,I just change the input from my TV from "S-VIDEO" to "antenna" and I will have TV (at least basic channels).well today I was sitting down watching TV,and I heard some hum.I started looking for the problem.I checked all the inputs.but nothing.until I disconnected the input from the dish receiver(the one that goes to the LNB)and boom! all the hum disappeared.what I noticed was the ground on the RG6 cable touching the the ground on the dish receiver produced the hum.so I cut the ground on the RG6 cable and the hum went away and I had TV and no hum.but I was not happy with the solution,so I kept looking for the source...
and I went to the cable (backup cable) the one that was connected to TV in case if a storm comes in. I unplugged it from TV and all the hum now is gone...
I think the ground from dish receivers and cable from modem were making a "LOOP".the hum was steady no matter what volume the amplifier was.
Do you think the problem is with the (CABLE) from the cable company? because I have a DVD player and a dish receiver connected to the amp and I do not have a ham or any noise at all,but as soon as I connect the cable for cable company to my TV the hum starts.have you ever had this problem guys?

[despotic931]

I once read an article explaining ground induced hum. Basically in a nutshell it said, "Just because two components are grounded doesn't mean it is a common ground" Perhaps it is just an issue with non-common grounds, either way that is a weird issue...

-Justin

[DigitalJunkie]

I've run across this several times.
Ground loops with the CATV coax are fairly common.

The cable drop will usually be grounded at the service entrance,Sometimes to the main ground-rod for the Mains service,sometimes to a separate ground (water spigot,pipe,separate ground-rod,etc.)
Not to mention being grounded at the distribution box on each block,and the grounds at all of your neighbors houses.Lots of potential for ground loops!

You could try using a couple of 75:300ohm baluns back-to-back on the CATV line,for some galvanic isolation.

[davidlzimmer]

I had the exact same problem with a gain clone based PC sound system. My TV tuner card had bad hum.

Solved the problem by mounting one of those cable grounding lugs directly to the PC cabinet. Hum is completely gone.

We owe you a thanks for starting this tread. I'm sure it will save others a lot of grief!