CurtPalme.com Home Theater Forum

Boilermaker · Joined: 21 May 2006 Posts: 527

A week ago a loud hum appeared on all channels of my HT audio system. I made no changes to cause it and it just appeared. In chasing down the problem I found it went away as soon as I disconnected the CATV line to my cable box. So I picked up a little CATV in-line hum eliminator and the hum disappeared.

The new problem I discovered Friday was that one of the channels (NCAA BB game) would not work. In fact, it was only one channel that would not work. So, I removed the hum eliminator, and the channel now works! WTF!!!

I assumed the hum eliminator is nothing but a series capacitor to block the low frequencies, but am I missing something here?

Thanks,
Bob

HK-Steve · Posted: Sun Mar 18, 2012 12:05 pm Post subject:

I had the same kind of problem,
I went to an car audio shop, picked up a stereo line isolator, has RCA plugs on each side. Solved my issue.

Something like the ebay link.

http://www.ebay.com/itm/Scosche-ES034-RCA-Ground-Loop-Isolator-Amp-Stereo-Signal-Noise-Filter-Suppressor-/120878069517?pt=LH_DefaultDomain_0&hash=item1c24e4f70d&vxp=mtr

Cheers

Boilermaker · Joined: 21 May 2006 Posts: 527

HK-Steve · Posted: Sun Mar 18, 2012 12:21 pm Post subject:

Yes it was, same issue of hum when connected, gone when dis-connected.
The output from my sat box is just stereo rca jacks, so was an easy fix.

Cheers
Steev

Boilermaker · Joined: 21 May 2006 Posts: 527

I'm using both the Toslink and the analog outputs for two different rooms, so I'm going to to disconnect the analog outputs to see it that will work.

Thanks,
Bob

**Curt Palme** · Posted: Sun Mar 18, 2012 12:56 pm Post subject:

If not, try a different brand of cable ground isolator. All are NOT made the same!

macgyver655 · Joined: 22 Aug 2007 Posts: 6959

Also, if the AC plug is 3 prong, try a 2 prong adapter.

Boilermaker · Joined: 21 May 2006 Posts: 527

Pulling out the analog didn't help - What is really wierd is that there is no hum in the analog system I'm using in my bedroom, but it is in my HT which is using the toslink!? All the equipment is located in the same rack, however.

**Curt Palme** · Posted: Mon Mar 19, 2012 11:45 am Post subject:

No, don't use the consumer stuff. Go to a satellite installer and ask to buy one. Worst case, I've got them here, but you should be able to get one locally. Look for something like the Holland brand, Blonder Tongue, etc.

Nashou66 · Posted: Mon Mar 19, 2012 12:13 pm Post subject:

Bob, Where is the distribution box/splitter for the cable Grounded? If its not grounded to the same side of your isolation transformer as the rest of your system a hum can develop. I had the same issue with my Sat box. I then ran a ground from the distribution amps for the sat dish's to the sub panel box and the hum went away. Might be the same thing.

Athanasios

Boilermaker · Joined: 21 May 2006 Posts: 527

**Curt Palme** · Posted: Mon Mar 19, 2012 3:40 pm Post subject:

Probably not. Ground loops can occur when changes are made somewhere in the cable line outside of the house, down the road or across the street somewhere. Different units route the ground differently as well, so it can change for the better or worse when the box is changed. Change the preamp or something in your a/v system, and that too can make it better or worse.

Boilermaker · Joined: 21 May 2006 Posts: 527

Ground loops can be a major PITA to find. The more complex the system, the more opportunity for a loop to occur, and mine is very complex. I'm just glad that this one is gone and I can still get all the channels.

I wish someone made an inexpensive converter that would convert the coax CATV to optical and then back to coax which would eliminate this problem and also eliminate lightning damage to equipment coming in on the coax.

Bob