dms8812 wrote:I have a hum problem with my home theatre system.
I have a Carver TFM-55X for my front left and right speaker systems, a Carver TFM-35X in mono mode for my subwoofer and a Carver AV-705X 5-channel for the 4 surround speakers and the center channel speaker. I use a B&K Reference 30 surround processor/preamp.
I use a Directv H20 satellite receiver and a Mitsubishi WD-57734 television.
The Carver AV-705X and the Mitsubishi TV do not have 3-wire grounded AC cords. The Carver TFM-55X, TFM-35X, the B&K and the Directv receiver DO have 3-wire grounded AC cords.
I am assuming the hum problem, which manifests itself in the center channel speaker system when I have the B&K in the surround mode, is an AC ground loop hum problem.
Would there be any danger in connecting the chasses of the ungrounded components to ground?
Lets start by assuming that you have separate electrical circuits involved with all the equipment. Are you sure that they are all properly connected, true 3 wire circuits or, if you have an older home, were some of the original circuits "converted" to 3 wire along the way? You can easily check thsi out by getting a ground fault electrical tester at your local hardware store (looks like a large 3 wire electrical plug with 3 colored LEDs on it) and testing each circuit for proper ground before calling in an electrician.
Second thing to check, before even attempting to attach a ground wire to all the chassis, use a simple electrical tester to make sure that each chassis is a proper ground to a known good ground, that each chassis shows zero resistance to each other and that there is no voltatge differential between each chassis.
Third thing to check is that those pieces of equipment have polarized plugs on them. May sound stupid, but a non polarized plug can be inserted in either direction into both a polarized or non-polarized wall outlet. If you have a non-polarized plug on the AV-705X (not supposed to, but you never know) or if the electrical circuit it is plugged into is wrongly wired, then simply reversing the way the plug goes into the wall could resolve your hum problem. If reversing the plug corrects your problem, call in an electrician to correct the problem with the house wiring.
Next step would probably be to check out all the interconnect wiring to ensure that its integrity is good.
If after all this you still have the hum problem, then it may be time to call in the big guns on here; the guys who really know what they are talking about. they may recomment power conditionners, ground fault isolators or all sorts of other solutions, so doing the simple checks I outlined above are the easy, low cost steps that you would have to do before shelling out a lot of money anyways. Just be methodical and thorough in your testing.
Over the years I've found that I have been able to resolve every ground induced hum problem with these simple steps for litterally hundreds of clients (mostly back when I was in electronics sales). We all take for granted that just because there is a 3 pronged socket on the wall that it is hooked up right. You'd be surprised at how often newly added on electrical circuits can be out of phase with the existing electrical circuitry, especially when they were not installed by a certified electrician.
Hope this helps.