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Irritating noise coming through speakers
liamoforange
post Jul 29 2012, 20:18
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Hi,

I am getting this annoying noise through my speakers. It's like there are crickets in my computer trying to send me subliminal messages in morse code.

A sample is attached.

1. It appears once the PC powers up.
2. It appears irregardless of what sound card is used either onboard sound, or external sound card
3. It appears irregardless of what slot external sound card is installed in
4. All cables are shielded.
5. I am running a cable to an external pre-amp and then to my amp.
6. When cable from PC is disconnected the pre-amp is dead silent, when attached the noise interferes with all functions. i.e. phono
7. When PC is off, no line noise on any channel in pre-amp.
8. Sound appears when using a different source, i.e. a receiver instead of pre and power amp.
9. Have swapped out multiple cables, even had a custom shielded cable made to run from PC to pre.
10. All drivers are installed properly and up to date.

Asus P5Q-deluxe
X-Fi Platinum sound card
Win 7 x64
4gb ram

Any and all help to troubleshoot and eliminate this problem will be greatly appreciated.
Attached File(s)
Attached File  Memo1.m4a ( 99.42K ) Number of downloads: 462
 
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Glenn Gundlach
post Jul 30 2012, 04:16
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You have a ground loop from hell. It's the kind of noise I've heard when the shield is not connected between units and the ground is coming from the power cords. If it were mine I'd begin by disconnecting as much as possible including the monitor. How many units use 3 wire cords? I can't tell you to run without grounds as a safety issue but temporarily lifting the ground for test purposes is OK. Are any of your shielded cable home made? Are the shields connected at both ends? Any units plugged onto a different power circuit?

G
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liamoforange
post Jul 30 2012, 06:12
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Thanks everyone, it is appreciated. I am going to try pulling the system apart and see what I can come up with for a solution, following some of the suggestions here.

A few additional details. This got markedly worse with the addition of a new modem to the system. It was there with the old modem, but about 5% of what is there now. That modem was failing and would not keep connected and needed replaced and the model is no longer available.

The "noise" (crosstalk?) gets worse the more data is coming down the line. If I am doing nothing online, it is minimal, surf it gets worse, stream live tv and it is pretty damn awful.

The entire audio chain is powered from dedicated sockets that have their own dedicated line from the fuse box.

The entire PC chain is powered from a Belkin UPS plugged into a different line from the box.

The only connection between the two parts of the system is the line out from the sound card to the pre-amp.

I have disconnected every cord in and out of the back of the PC save for the line out to the pre-amp, the power cord, and the line in from the modem. Makes 0 difference.

I did move the modem to another part of the room, about 25' away but it made no difference.

I have plugged other pieces, ipod and cd player, into the pre-amp and the noise is there with all of them if the line from the PC is connected, even if other line out selections are made. Disconnect the PC cable it goes away.

Keep firing suggestions for when I can take the day and rip this apart.

One other thing, I have bought an E-mu 1616M PCI-e with a separate break out box. I really don't want to eat the cost of it by opening it if this problem cannot be resolved. Would the grounding in that sound card/breakout box eliminate this situation?

Finally, could it be a failing part in my PC that is causing this?

Thank you. smile.gif

This post has been edited by liamoforange: Jul 30 2012, 06:15
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mzil
post Jul 30 2012, 23:03
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QUOTE (liamoforange @ Jul 30 2012, 01:12) *
...The entire audio chain is powered from dedicated sockets that have their own dedicated line from the fuse box.

The entire PC chain is powered from a Belkin UPS plugged into a different line from the box. ...

...

I have disconnected every cord in and out of the back of the PC save for the line out to the pre-amp, the power cord, and the line in from the modem. Makes 0 difference.
[emphasis in blodface by me]

Ground loops are caused when there are two or more "ground potentials" connected to the same device and not limited to AC ground wires but rather ALL wires. Adding transformers to isolate the problem works, but it is a band-aid approach and may degrade the sound (notice that advertised one makes no claims as to a flat response below 40 Hz). The better approach, if at all possible, is to reconfigure the system so all your devices receive their ground from the same EXACT source (called a "star grounding" topology) like one large power strip plugged to a singular AC outlet (UPS allowed, as long as it doesn't also connect to telephone/internet/cable etc. too), and then apply any isolation transformer devices, only if still needed, to things like the wire that feeds the modem the internet.

I have placed in boldface the probable problems with your setup. You mention using different outlets and by leaving the modem attached you have a new, alternate ground source (potential), the wire for the, I assume, cable company wire.

Disconnect that cable wire, in addition to using a star grounding design, and if that's indeed the problem wire, the correct transformer to buy for it is this .

EDIT TO ADD: Yikes, that price is ridiculous! I buy them for $10 to $20 USD usually. I'm hunting for a better source and will report back, but I'l leave the link as is, for a picture reference only, for now.

This post has been edited by mzil: Jul 30 2012, 23:21
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mzil
post Jul 30 2012, 23:13
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OK, here's a more reasonable price with free shipping.

Many places that sell it don't even mention the ground breaking aspect and simply refer to it as a "surge protector" but if you read the outer casing you'll see it is.
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liamoforange
post Jul 30 2012, 23:42
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QUOTE (mzil @ Jul 30 2012, 17:13) *
OK, here's a more reasonable price with free shipping.

Many places that sell it don't even mention the ground breaking aspect and simply refer to it as a "surge protector" but if you read the outer casing you'll see it is.


Hi, thanks but I think there was some confusion there. I am using a DSL modem, not a cable modem. I don't think that part will work with my current configuration.

I will try getting everything on the one circuit and see if I can eliminate the noise that way. Short term I have a solution that will keep me sane, but considering I installed dedicated lines for my audio gear in the room I will need to find as organic a solution as possible.

smile.gif
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mzil
post Jul 31 2012, 00:13
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Oh, OK, I don't know off the top of my head the correct device to break the ground connection from a DSL line, however if you simply disconnect it from the back of the PC, as a diagnostic test, as well as use star grounding [or what the attached link calls "single point" (like the rays of a star leading to its core)] I'm confident you wont have to use that RCA in line device and hence not worry about any possible compromise in sound performance it may invoke.

Eliminating Hum and Ground Loops

This post has been edited by mzil: Jul 31 2012, 00:17
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