Ground hum

[Infredible]

Hi! I'm new here.

I just moved home and got new dishes installed Sunday using the Dish mover program.

I have 110/119 and 148 Dish Pro and a DP34 connected to my 921 all RG6 cables running about < 100 feet. I have a high end sound system. Since the install I'm battling with a 50Hz hum which has never been there before.
After investigation I found that If I disconnect both feed to 921 the hum goes away. The installer did grounded the dishes to a water pipe.
I tried disconnecting the dish ground but the hum is still present.
All my gears are plugged in the same outlet.
Do you guys have any ideas why that install introduced the hum.
I had four previous dish install before and never came across this problem.
Thanks.

Fred.

 

[bweiteka]

does the hum originate from you 921 box or from the speakers in your a/v system?

 

[Infredible]

The hum comes from the speakers and with any input selected on my preamp..

Fred.

 

[Mark_AR]

If you aren't too familiar with electicity or wiring, I would refer it to a qualified electrician.

First, if possible, see if the cables from the dish/switch run side-by-side any of your house electrical wiring. If so, the hum 'might' be from something called 'induction'. Moving the cables away from electrical wiring may solve it.

Grounding to a water pipe isn't always a proper earth ground, but you stated that removing the ground didn't help.

Sooo....

I had an issue similar to this when I first got my 921. The hum was originating from ground differential of the HDTV through the 921 and would cause me fits.

Check to see that your outlet is wired correctly. You can get an outlet tester that plugs into your outlet and has indicator lights. You can get them at any hardware store for a few bux and that will tell you if the outlet you are using is correctly wired and/or grounded properly.

Older houses may have 3 prong outlet plugs but that copper ground wire may not even be hooked up. If the tester indicates the outlet is wired properly then keep going. If not, call an electrician.

Try disconnecting TV from 921 and everything else from your stereo so that all you have is a direct link from stereo to 921 and nothing else.

Hum or no hum?

If hum:
I am not sure why there is an open ground difference somewhere. Does the stereo have a 3 wire plug or 2?

Try running a single wire from the metal case of the 921 to a chassis ground(metal part) on the stereo.

If no hum:
Shut everything off and then connect the TV. IF the hum comes back, then you have your hum source.

To fix it, I used a cable between Co-ax (RG59)TV in and 921 (Co-ax out) even though my 921 uses DVI-D cable to my HDTV, I use the coax as a grounding equalizer.

This made sure that my TV, 921 and stereo were all connected to the same ground.

I've since changed my audio amp and now use digital optical TOS-LINK to connect audio so it doesn't matter about ground differential, but I still have everything grounded together.

Hope this helps....

 

[Infredible]

Mark_Ar,

Thanks for the tips. I'm going to check all the above. I'll report back my finds.

Fred.

 

[supereal]

Most, if not all, hum is produced by a difference in potential at two or more grounds. Using a line conditioner or an uninteruptable power supply between AC input and the device can often cure it.

 

[Bradtothebone]

Hi! I'm new here.


After investigation I found that If I disconnect both feed to 921 the hum goes away. The installer did grounded the dishes to a water pipe.
I tried disconnecting the dish ground but the hum is still present.
All my gears are plugged in the same outlet.

Fred.

Fred,
First, welcome to the forum! Mark_AR's suggestions are all good, but let's clarify something first: You say the Dish is grounded, but are the two Coax feeds grounded at a ground block (preferably before they come into the house)? Ideally, they should be grounded to the same point as the house's electrical system ground to prevent ground loops. If you remove the sat feeds and the hum stops, it almost has to be something to do with them.

Brad

 

[DucTape]

Hi! I'm new here.

I just moved home and got new dishes installed Sunday using the Dish mover program.

I have 110/119 and 148 Dish Pro and a DP34 connected to my 921 all RG6 cables running about < 100 feet. I have a high end sound system. Since the install I'm battling with a 50Hz hum which has never been there before.
After investigation I found that If I disconnect both feed to 921 the hum goes away. The installer did grounded the dishes to a water pipe.
I tried disconnecting the dish ground but the hum is still present.
All my gears are plugged in the same outlet.
Do you guys have any ideas why that install introduced the hum.
I had four previous dish install before and never came across this problem.
Thanks.

Fred.

Maybe check that the installer grounded at the switches they installed which is I believe how they ground the coax lines. I had a similar problem when I had cable.

 

[Craig Henrikson]

If you aren't too familiar with electicity or wiring, I would refer it to a qualified electrician.



I've since changed my audio amp and now use digital optical TOS-LINK to connect audio so it doesn't matter about ground differential, but I still have everything grounded together.

Hope this helps....

I note that my 811 was happy to provide hum (60 Hz) even thru the optical feed. I sold it!

 

[TuxCoder]

I note that my 811 was happy to provide hum (60 Hz) even thru the optical feed.

I can see that maybe happening for digital audio as encoded to PCM by the 811 for analog stations only, but even then it's a stretch... for all other channels, though, there shouldn't be any locally induced 60Hz hum through digital audio (copper OR optical).

 

[SimpleSimon]

I can see that maybe happening for digital audio as encoded to PCM by the 811 for analog stations only, but even then it's a stretch... for all other channels, though, there shouldn't be any locally induced 60Hz hum through digital audio (copper OR optical).

Sure there can - if the interference is whacking the groundplane of the receiver's circuit board, the 60Hz (not 50Hz) can show up anywhere - video or audio.

 

[TuxCoder]

Sure there can - if the interference is whacking the groundplane of the receiver's circuit board, the 60Hz (not 50Hz) can show up anywhere - video or audio.

I'll give you that if by "receiver" you mean the audio receiver. Any interference present on the 811 side would not be carried over the optical connection since (a) it's optical and (b) it's only doing a data transfer of the demultiplexed audio stream (when tuning to a sat or digital OTA station). The digital coax connection could be susceptible to the 60Hz electrical interference but it would definitely not be evident as a 60Hz hum on the audio receiver. Instead, only if the interference is bad enough, it would cause cutouts, chirps, pops, etc.

If the 811 is tuned to an analog OTA station, then it is the one doing A-D conversion and encoding the audio to PCM, so possibly in the analog side of that hardware you could pick up interference. And of course, on the audio receiver end you could pick up the interference as well on its analog side (after the DAC).

And true, if the original poster is actually getting 50Hz, then San Francisco is apparently also some European city (or some other parts of the world).

 

[Infredible]

Fred,
First, welcome to the forum! Mark_AR's suggestions are all good, but let's clarify something first: You say the Dish is grounded, but are the two Coax feeds grounded at a ground block (preferably before they come into the house)? Ideally, they should be grounded to the same point as the house's electrical system ground to prevent ground loops. If you remove the sat feeds and the hum stops, it almost has to be something to do with them.

Brad

My bad, the two coax are grounded outside to a water pipe which I believe is not the proper way of grounding. I will try to ground the coax to a "real" ground from the house main.
I tried disconnecting that ground but the hum is still here and additional radio noise comes in too.

My mistake about 50Hz, I come from Europe so I'm spoiled

Fred.

 

[SimpleSimon]

Tux - good point about the hum not able to hit a audio signal that's digital from before the box to after it. So, we need to know what type of channel is affected.

 

[Infredible]

I fixed my hum problem, it was coming from my EQ which is a pro gear with balanced input. A trip to RadioShack where I brought a ground lifted AC prong for my EQ and an isolation transformer that I connected between the receiver and EQ. Everything is now dead silent.

Fred.