Ground loop isolator

[TLKLane]

I just noticed at the Polk Store a "Hum Stopping Ground Loop Isolator" for sale. (model: Jensen VRD-1FF ISO-MAX). My electronics knowledge is very limited but I would like the cleanest sound and picture I can find. Currently using digital cable and internet. I can't seem to find any consumer friendly language to explain exactly what this does. Can anyone explain in low-tech-talk what it should do? Already had the cable guy install a small line amplifier.

Thanks,

Ted

[burdette]

A ground loop can develop if not all of your components are grounded at the same electric potential. The result is a hummm that corresponds (usually) to the 60Hz AC line voltage. If you don't actually hear a hummm, you probably don't need a fix (I'm sure others may disagree... buy one anyway if you want the warm fuzzies).

The problem usually stems from having more than one component earth grounded (i.e. connected to AC via a 3-prong plug). TV can also be the culprit via cable ground providing the extra grounding path. In some circumstances, even a metal equipment rack can cause the problem.

If you actually have a hum, check to see if you have more than one component earth grounded. If you do, change your setup so only one is grounded (i.e. plug only one 3-prong plug into the wall, use cheaters on all others).

If that doesn't do it and you have a TV connected to your system, disconnect the cable TV line and see if that does it. If the TV is connected through a VCR to your system, it could still be the problem.

Don't know how much Polk is charging... I know you can pick up isolators for under $10. Edit: that would be an audio isolator, if the hum is not in your cable.

Edit: if you're talking about that $55 job, AND you have a hum, I'd check the AC power before dropping that money. Also, you can make the video isolator using two 75ohm to 300 ohm converters, connected 300ohm to 300ohm. The manufacturer sells the $55 deal for $52.. odd.

[wlrandall]

Have to agree, if you had it, you would definitely know it.

Wally

[schumach]

You can have more than one device in your setup grounded as long as the two devices that are grounded are not connect to each other with a cable that provides the grounding path between the two devices.

Example:
1- Using RCA plugs between a DVD player and receiver will provide a ground path between the DVD player and receiver, so only one device needs to be grounded.

2- Using an optical cable between the DVD player and the receiver does not provide a ground path between the DVD player and receiver. In thiis case both devices can be grounded and not cause a ground loop.

[TLKLane]

Thanks for the posts! I think I understand the theory and attempts to get rid of any"Hum" sound, but what about the picture clarity? Should this device help eliminate"noise, i.e. possible ghosting" in the picture. As I mentioned I have digital cable but only for the premium channels. I was told by the cable guy that everything else is still analog.

Thanks

___

for those interested

Mitsubishi 55' widescreen
Denon 2802 receiver
Panasonic DVD
Mitsubishi VCR
Polk Rt1000 fronts
polk CS400i center
Polk FX500 surrounds
no sub or rear channel... yet!

[wlrandall]

You are correct, they are for audio hum only. If you have ghosting, that is a separate issue. Ghosting is usually caused by too strong a signal or reflection of such, i.e. water tower in signal path of antenna. I don't think you need the amplifier. Furthermore, I wasn't at all impressed with digital cable, even on a 27". Ended up with DirecTV and have much happier except with local channels. They use waaaay too much compression on them and the picture stinks.

Wally