Plate amp ground loop problem

eric nyhof · 11-14-2004, 02:08 PM

I am in the process of building a Stryke thunder 12.3 with the PE 500 watt plate amp. The driver is on back order but I have the amp already and decided to play around with it.
I hooked it up to my receiver (pioneer 1014) and took the subwoofer out of my truck and hooked it up. The result was a loud hum from the subwoofer and makes its back into my receiver and through my mains.

I unhooked everything from my reciever and with just a cd player there is no hum. Putting everything back one piece at a time resulted in the problem coming from my satallite line. The line that runs from the dish to the receiver is causing the problem. The line is grounded to a water pipe, and to make sure I took another wire and ran it to a real electrical ground, and the hum remains.

Switching power plugs also has no effect. I currently have a crappy aiwa subwoofer hooked up and there are no problems.

Has anybody else had a problem like this , or know how to fix it?

MichaelAngelo · 11-14-2004, 02:28 PM

Eric,

I had a similar problem with my cable. After some Googling, I found a tip that worked for me. I ran the cable line into 2 75-300ohm converters back to back 75-300-back to 75. I used the little "pigtail" type. This cured my hum. I don't know if it will work with satellite though-worth a try.
Also, I've seen people use a 2 prong adapter plug to elimninate ground loop hum.
Radio Shack sells special RCA cables that reduce hum.
HTH

chris_steltz · 11-17-2004, 11:08 PM

I have the exact problem as we speak. Everything is fine until i hook the sat line up to my tivo then i get hum everywhere. I tried a ground loop isolator but it did not work with sat. So as of right now im just hooked up to the TV directly and my amps have to be off when im watching it.

Greg Yeatts · 11-18-2004, 09:29 AM

I have ground loop hum from the mains in my 1014TX as well. Actually, I have humming everywhere... my TV, sub mains from the 1014TX. Part of the ground loop hum went away when I turned off a flourescent light in my kitchen. Why? Who knows. I think the rest of my problem is from my cable line. Maybe if I did not have my VCR hooked into the system everything would be ok. We shall see.

I had the same problem when I introduced an Xbox into my old surround sound system. I made lots of changes and the humming went away. Not sure which change worked though.

I am more than happy with the performance of the 1014TX though.

Wayne A. Pflughaupt · 11-18-2004, 12:06 PM

Eric,

Quote:

The line is grounded to a water pipe, and to make sure I took another wire and ran it to a real electrical ground, and the hum remains.

There’s your problem right there. You have two grounds – that is what causes ground loops. The dish should be grounded at the same place that all the other equipment in the HT is grounded to – which is the ground stake at the breaker panel. So, eliminate the one to the water pipe – that may be all you need to do.

Greg,

Quote:

Part of the ground loop hum went away when I turned off a flourescent light in my kitchen. Why? Who knows.

It could be because your gear is on the same circuit as the light. Or, because the kitchen light circuit is on the same service leg as your gear. It sounds like you’re a good candidate for a dedicated circuit for your home theater system.

Regards,
Wayne A. Pflughaupt

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Greg Yeatts · 11-18-2004, 03:49 PM

Wayne

I have read that if I plug all of my gear into the same outlet the problem will be taken care of. I may try to run an extension cord from my subwoofer amplifier to the rest of my gear. Currently my sub sits a little out of cord reach of the rest of my gear. Since the sub has a 1,000 watt plate amp I will need to use an extra heavy duty extension cord. I think I can find one at the BORG.

Greg Yeatts · 11-20-2004, 11:57 AM

Update

I plugged all my gear into the same outlet with heavy duty extension cords. I still have the ground loop. So, I went to rat shack and bought a 75ohm to 300 ohm converter (transformer) and then a 300 ohm to 75 ohm converter. I plugged my cable into the 75 ohm to 300 ohm converter and then converted the 300ohm back to 75 ohm. Then I plugged this into my VCR. Almost all of the hum is gone. If you put your ear right up against the mid with the volume maxed you can barely hear it. Since this is not my usual seating position this is not a problem.

All of the converters did add a lot of noise to channels 75 through 78. I think I will order a proper video isolation transformer from PE to see if I can fix the problem. I have read on the net that my cable company should be willing to fix this problem.

If I turn my TV off (not an option with HT) I have no hum whatsoever.

MichaelAngelo · 11-21-2004, 02:13 PM

Wayne A. Pflughaupt · 11-21-2004, 10:47 PM

Quote:

I have read on the net that my cable company should be willing to fix this problem.

Hate to be the bearer of bad news, Greg, but I wish you luck with that. I called my cable company once with that complaint and the technician that came out said with a straight face, “Typically when we have this problem it’s because of the customer’s sound system.”

Regards,
Wayne A. Pflughaupt

eric nyhof · 11-23-2004, 09:05 PM

Well,
Last night I decided to get a line conditioner. Got the monster power HT800 and ran my satellite line in the thing and out to my receiver an the problem is gone.
I figure I probably needed a decent power strip anyways.

aaron_d · 11-24-2004, 09:34 AM

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