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In , on 02/19/04
at 12:48 PM, (Brian) said:

(Brian) wrote in message
.com... Thanks to
the group for all the excellent advice. I am clearly trolling in the
right waters.

This is an update on my progress: I disconnected ALL leads from the
receiver other than the subwoofer cable. I unplugged the receiver's
powercord from the AC outlet. I removed the receiver to a new room,
away from all other wire and hardware. I place the receiver in the
middle of the floor (still not plugged to AC), connected the subwoofer
and turned on the subwoofer. Hmmm? Hummm! Touching the receiver's
case slightly altered the pitch of the hum. When I plugged the
received into the same outlet as the subwoofer, the hum increased in
volume, and loudened again when I powered on the receiver.

(All: Is it possible that a ground loop is being set up between the
receiver's subwoofer output jack and the receiver's case? With a
receiver that isn't even plugged into an electrical outlet?)

"Ground" is a relative thing, usually implying "zero" potential, but
"zero" is not an absolute. Think of a chair. You can measure the height
of a chair by sitting it on the ground and measuring the distance
between the ground and the top of the chair seat. Now move the chair to
the 10th floor of a building. What is the chair height now? How would
you measure it? Generally, we would measure chair height from the
surface the chair sits on and everything works out. However if the
surface is not level or not flat, there could be some unwanted chair
movement. Because I want to use the concept below, consider what could
happen to our chair if our perfectly flat floor is distorted by a
nearby heavy appliance.

The electrical "ground" in your home is usually a metal rod driven into
the earth near the electrical panel. Each piece of your audio equipment
keeps an eye on that ground so that it knows what "zero" means in the
context of your home. (Your next door neighbor could have a slightly
different ground.) When you connect units together in your stereo, each
unit assumes that it and all the other units reference the same ground.
If the ground in your home is stressed by a large appliance, the units
in your stereo might see different grounds. This will cause unexpected
current to flow in the ground and trouble is likely.

Consider what could happen if your receiver is sending out zero (the
output voltage of the receiver is the same as the receiver's ground).
If the subwoofer's ground is the same as the receiver's, the the
subwoofer agrees that the input is zero and there should be no sound.
If the subwoofer's ground is different from the receiver's ground by
0.05, then the subwoofer will think the receiver is sending 0.05 when
the receiver thinks it is sending 0.00. The subwoofer will amplify that
0.05 and you'll hear whatever trash is circulating in the ground.

Note the above discussion is a small tip of the iceberg. Whole books
are written about grounding.

(Robert B: Wish I knew how to lift the ground using an extension cord. You
all are too smart for me.)

Use one of those "cheater" adaptors designed for connecting a three
prong plug to a two prong outlet and don't connect the green wire to
annything. Some high end audio components have a switch designed to
accomplish this.

(Troy: hope its not speaker wire interference, because the speaker
wires are 30 feet away.)
(Todd, Neil and Arny: I am using same outlet. I've removed about all
I can remove from the system, including tv cable in. What I have
configured is: electric
outlet-to-power-cord-to-subwooder-to-cable-to-receiver to an electric
cord either (a)laying on the floor or (b) plugged back into the same
outlet as the subwoofer.

Good. This minimizes (but does not eliminate) the possibility of a
ground loop. (Poor design can create ground loops inside a unit) (an
improperly designed unit may pollute the ground and cause trouble for
other units in the system)

(Randy: I take your meaning about the 3 light tester not being the
end-all. Beyond that, you're beyond me. But I stripped down pretty
much to my skivvies here.)

This is a good start. (Don't stand near the window in your skivvies or
we'll be seeing you on the news.)

(Barry: this is more than a little hum. It overpowers the other 5
speakers, even with the gain on the subwoofer fairly low. The jack of
the receiver didn't separate, but the plug end of the connecting cable
came apart. The sheath, pin and some plastic stayed on the receiver
jack, while a small metallic clip and some more plastic stayed on the
wire. And yes, I am thinking that maybe I did damage the receiver
jack. I'm trying the eliminate other potentials before taking my
Onkyo into the shop.)

It is very likely that you broke the outer part of the subwoofer jack
on your receiver. If this is so, then you will probably pick-up some
noise.

I am not surprised that you hear some noise when the receiver is turned
off or not plugged in to the power outlet. This is another issue and we
can deal with it separately (if necessary) after we solve the more
urgent problem of the loud hum.

For a test, pick another output jack on your receiver that is not
adjacent to your subwoofer jack (adjacent jacks could also have been
damaged by the same event). Make sure that the subwoofer is turned off
and its level control is turned down when you do this. You can use REC
OUT if you like (if you do use REC OUT, turn the selector switch to CD
and make sure your CD player is ON and in the STOP mode) If the
subwoofer hum is now gone (don't forget to turn the subwoofer ON and
turn up its level control), then you have a damaged subwoofer output
jack.

Sometimes sniffles and a cough aren't a cold. Sometimes it's an
pneumonia.

Or allergies and someone will claim it's a government plot.

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wordgame:123(abc):14 9 20 5 2 9 18 4 at 22 15 9 3 5 14 5 20 dot 3 15
13 (Barry Mann)
[sorry about the puzzle, spammers are ruining my mailbox]
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