Hiss/Ground Loop..Need Some Help

wingnut4772

Hi guys. I am still trying to iron out the last bit of noise from my system and the Earthquake Guys suggested trying a ground wire from my pre to the amp as I have pretty much narrowed it down to the pre. Mind you it's miniscule but I want perfect.:p

My question is : my pre has a ground chassis connection but the amp does not...so where do I attach the ground to the amp?

F1nut

First off, is it a hiss or a hum as it makes a difference as to a possible solution.

wingnut4772

both. It is slight but it is magnified somewhat when the pre is turned on.

F1nut

Hmmm....well a slight hiss from your tweeters can be normal, but a hum isn't. Try running a wire from the ground screw on the pre to a chassis screw on the amp. Make sure the wire contacts bare metal on the amp.

wingnut4772

F1nut wrote:

Hmmm....well a slight hiss from your tweeters can be normal, but a hum isn't. Try running a wire from the ground screw on the pre to a chassis screw on the amp. Make sure the wire contacts bare metal on the amp.

Ok. Any screw on the amp chassis? It does not matter where?

F1nut

Any screw on the back should ground to the chassis.

wingnut4772

Ok. Further exploring is telling me it's the Satellite. Funny thing it is only going away when I remove the HDMI cable from the Sat box..not the actual cables coming in from the outside...?

Even at full volume I have to have my ear right up against the speaker to hear it but still.. I 'd rather it go away. All the other inputs are fine.

F1nut

Ground loop hum seems to be a fairly common problem with those satellite boxes. You'll need an isolation device for the box. Polk sells one, but I'm sure you could find one locally, maybe Rat Shack.

BlueMDPicker

Did your satellite provider use a ground separate from your house electrical service ground? If so, that could cause the problem.

adam2434

Posted this a while back. This isolator did a nice job of eliminating the ground loop hum from my cable TV. Polk sells one for around $50. This one is only $12. I don't know what the differences are, but this $12 one did the trick for me.

http://www.polkaudio.com/forums/showthread.php?t=43938&highlight=cisp

wingnut4772

Thanks. I read somewhere that that does not work on Sat...? I looked at the box on the side of the house where they seem to have all the Sat cables and the green wire is not connected to anything.

gregvet

The green wire on my satellite cable is connected to a copper rod in the ground.

polkatese

Darla, the green wire has to be connected to the common ground in the box (which usually there on newer houses). The guy who installed mine "preached" about this, noting that some sloppy installers (which DirecTV has known to sub these jobs out to) will skip this part.

BlueMDPicker

wingnut4772 wrote:

Thanks. I read somewhere that that does not work on Sat...? I looked at the box on the side of the house where they seem to have all the Sat cables and the green wire is not connected to anything.

Many (probably more like most) installers drive a copper rod near the foundation and in close proximity to the coax entrance point. Yep, that's a ground--but, it's at a different potential to your electrical service ground. No big deal until you start grounding other components in the signal path. The two grounds, seeking to balance potential, set up a hum.

If your sat block isn't grounded to anything, try finding an easy point inside the house, using a splitter with ground, to attach to the green ground in a duplex receptacle.

wingnut4772

I attached the ground from the Sat.cable to the house ground and it made it slightly worse.

BlueMDPicker

Now, use cheater adapters (three in, two out) to find the looping device. When you find it, get something like the PS Audio PCs with removable ground pin for a permanent fix.

wingnut4772

Well FPL came out to the house and told me that I have the old water ground and not the 'two stake' kind. I have an electrician coming out to update my ground. Would this make a difference with that annoying little hiss and hum? Nothing else I do seems to eliminate it totally.

BlueMDPicker

How many of your components are grounded (all three prongs intact)? Since you physically ground the components together via interconnects, it's really only necessary for one of the components to have a power plug ground--usually the amplifier/AVR is best IMO. Did you try cheaters on the components to see if that impacted the issue yet?

wingnut4772

Yes. I tried everything and it's still there. Its miniscule..but there.