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From: Jerohm on 22 Jan 2008 11:26 I figured out how to stop the hum, but I don't really understand what is going on. The AC adapter has a three prong grounding plug. If I use one of those 'cheater' plugs and don't connect the ground - NO HUM!! Counterintuitive huh? I have as many 3 prong devices as NOT, associated (read: connected) to my Home Theater equipment that don't cause problems. Anybody smarter than me that can enlighten me? Thanks
From: Pen on 22 Jan 2008 12:13 Jerohm wrote: > I figured out how to stop the hum, but I don't really understand what is > going on. The AC adapter has a three prong grounding plug. If I use one of > those 'cheater' plugs and don't connect the ground - NO HUM!! > Counterintuitive huh? I have as many 3 prong devices as NOT, associated > (read: connected) to my Home Theater equipment that don't cause problems. > > Anybody smarter than me that can enlighten me? > Thanks > > The most likely cause is a ground loop. A high resistance between 2 grounds. To actually find this is probably going to be fairly difficult. Somewhere there's a ground not making good contact. You'll have to check the circuit in question all the way back to the Fuse Box.
From: Sjouke Burry on 22 Jan 2008 19:50 Jerohm wrote: > I figured out how to stop the hum, but I don't really understand what is > going on. The AC adapter has a three prong grounding plug. If I use one of > those 'cheater' plugs and don't connect the ground - NO HUM!! > Counterintuitive huh? I have as many 3 prong devices as NOT, associated > (read: connected) to my Home Theater equipment that don't cause problems. > > Anybody smarter than me that can enlighten me? > Thanks > > What you had was a ground loop. If you want trouble free operation between audio/video and computer hardware, work as mush as possible from 1 wall outlet only. Between grounds of different outlets there can be several millivolts because of voltage drop on the return wire, and there might be a mix up in the house wiring between ground and return, in some countries the ground and the return wire are even connected in some places, and is a sure source of hum. By using the cheater plug, you opened the ground loop, and use the ground of the system you connect to only. Best way is not to cheat, but use only one wall outlet for computer and your device.
From: Barry Watzman on 24 Jan 2008 00:48 Re: "in some countries the ground and the return wire are even connected in some places" In all countries, actually, as far as I know .... but NOT at the individual outlets. In the US, Ground (green) and Neutral (white) (which you call return) are [supposed to be] connected together at 1 and only 1 point in each building, at the "service entrance" (usually, but not always, that is the main master fusebox or breaker panel). Sjouke Burry wrote: > Jerohm wrote: >> I figured out how to stop the hum, but I don't really understand what >> is going on. The AC adapter has a three prong grounding plug. If I >> use one of those 'cheater' plugs and don't connect the ground - NO >> HUM!! Counterintuitive huh? I have as many 3 prong devices as NOT, >> associated (read: connected) to my Home Theater equipment that don't >> cause problems. >> >> Anybody smarter than me that can enlighten me? >> Thanks >> > What you had was a ground loop. If you want trouble free > operation between audio/video and computer hardware, > work as mush as possible from 1 wall outlet only. > Between grounds of different outlets there can be several millivolts > because of voltage drop on the return wire, and there might be a > mix up in the house wiring between ground and return, in some > countries the ground and the return wire are even connected in > some places, and is a sure source of hum. > By using the cheater plug, you opened the ground loop, and use > the ground of the system you connect to only. > Best way is not to cheat, but use only one wall outlet for computer > and your device.
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