High pitched hiss from PC - AVS Forum
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post #1 of 31 Old 01-10-2013, 02:28 PM - Thread Starter
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Hi guys,

I have the following setup:

PC ---HDMI---> Denon 4311CI (as preamp) ----RCA---> W4S MC3x500 (amp) ----> speakers

(As well as some speakers being amplified by the receiver, but those aren't relevant here)

While the amp is on, I get a high pitched hiss from the speakers. The volume I put the preamp at is irrelevant--it can be turned off and the noise is still there.

I can unplug the preamp and the noise is still there.

If I unplug the HDMI cable from the PC, the noise goes away.

If I touch the front of the HDMI cable to the back of the preamp (just metal to metal, not near the HDMI socket), the noise returns.


The HDMI out on my PC is running from an Nvidia GTX 460.



Does anyone have any advice on what I could do to reduce or eliminate this noise?
I can (barely) hear it from my listening position, but it is still annoying.


Thanks!
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post #2 of 31 Old 01-14-2013, 08:23 AM - Thread Starter
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Anyone? If no one here has any ideas, any suggestions on where else I should post?

Thanks!
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post #3 of 31 Old 01-14-2013, 08:48 AM
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Could it be a ground loop issue? Try disconnecting any coax lines from their source and see if it goes away.
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post #4 of 31 Old 01-14-2013, 08:58 AM
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Quote:
Originally Posted by TKEBH964 View Post

Could it be a ground loop issue? Try disconnecting any coax lines from their source and see if it goes away.
+1.

- On the HTPC, disconnect everything from the preamp and TO the HTPC (like coax cables, antennas etc. Hell, even the network cable)
- Connect only the HDMI to the Denon - Do you get the hiss?
- If yes - Try a different HDMI cable and/or different input on the 4311? (It has plenty)
- If no, start connecting other things from/to the HTPC one by one and find the offender.
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post #5 of 31 Old 01-14-2013, 09:50 AM
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How is the HTPC plugged in power-wise? UPS, surge-protector, direct to socket?

What else is running on that circuit? Something is creating a ground loop to your AMP.

Can you connect the PC to the AMP directly via analog connections? If so, see if the hiss goes away (or becomes a hum).

Alternatively, you could try powering the speakers (temporarily) from the AVR itself to see if the same noise is there.

How are your amp/speakers connected (two conductor, Balanced/XLR, coat hanger)?

For your PC silencing needs...check out www.silentpcreview.com

For your WHS needs...check out www.wegotserved.co.uk
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post #6 of 31 Old 01-14-2013, 01:51 PM - Thread Starter
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Thanks for the suggestions, I'll give them a shot and see what happens.


Here is a more detailed layout of what is going on:


Circuit 1 (20A):
- the amp for the 3 front speakers

- a UPS powering the below (maybe run through a power strip, I forget... can check. If so the power strip may be handling the things I don't care about having on the UPS)
- PC
- 30" monitor
- printer
- FIOS router
- MoCA adapter for TIVO (cables in to the router via ethernet & coax)
- a set of speakers on the PC side of the room (logitech something or other, 5.1)

Circuit 2 (20A):
- HDTV
- Denon 4311CI
- 2 Rhythmik F15HP subwoofers
- PS3
- XBOX 360
- FIOS set top box


I tried plugging the Denon into circuit 1, but that didn't help. (I figured it wouldn't, since the noise came through even when the Denon was unplugged)

Also note that the noise comes through just from touching the PC cable to the receiver (in a spot that conducts)--it doesn't have to be plugged in to an HDMI slot.


Will try isolating the PC to see if its something external, or something in the PC itself.
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post #7 of 31 Old 01-14-2013, 02:10 PM
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- Unplug PC from UPS and direct into Circuit 1 (or 2) and see if you still get the whine.
- Unplug anything from the UPS that is connected via coax cables (router, Moca adapter), while leaving the PC connected and test for whine.
- Get a coax grounding strip, plug that into the UPS, plug the coax into the strip, from the strip to the devices, test.

test test test....no other choice. You have a loop going on somewhere. smile.gif
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post #8 of 31 Old 01-14-2013, 06:42 PM - Thread Starter
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Ok, I did some testing.

The high pitched whine is from when my printer's USB cable is in the PC, and the printer is on.

However, even with the printer disconnected, there is some variable noise/static that isn't there when the PC isn't connected. (When PC is disconnected, there is hiss/static still, but quieter and not variable)
Moving the PC power plug didn't help that I could tell.

I'll play around with it more later, but for now, I'm happy enough with the printer powered off.
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post #9 of 31 Old 01-14-2013, 08:18 PM - Thread Starter
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Argh, nevermind, its still here.

The high pitched sound went away for a short time when I unplugged the printer, but is now back. I tried disconnecting everything from the PC, its still there.

With the PC unplugged, I still have a minorly annoying sound, but not nearly as bad as when the PC is in. And it changes when I open really intensive stuff on my PC--furmark (a GPU load testing tool) causes a very fast, relatively quiet (but certainly noticable) thumping noise (sort of... its relatively low pitch, like a rurring sound) to come from my speakers (either as the GPUs suck up more juice, or as their fans go nuts. I think the former.)

Loading the CPU also causes noise changes: it completely hushes the sounds down to as if the PC were unplugged. E.g., running intel burn test with all 4 cores active shuts off the noise.

And scrolling my bluetooth mouse's scrollwheel while viewing a webpage causes some sounds too (static), but only on certain webpages. Others I can't hear it, or I barely hear it. Sounds almost like when you are right next to a computer and you load the CPU--that kind of whirring static sound.

Its hard to swap things around in the circuits for more extensive tests because circuit 1 only has 1 outlet right by the PC, while circuit 2 is every other outlet in the basement.

I guess the next thing to try is having everything on the same circuit and seeing if the noise is different?

EDIT: Ok, moved PC & Amp to circuit 2 with the receiver. A couple differences:
- the high pitched whine is a little worse, I think. But only when the PC is actively being displayed via the receiver--otherwise its better than before. (This doesn't help me though, as the vast majority of my usage is via PC). With the PC & Amp on circuit 1, the noise was the same regardless of whether the PC was displayed via the receiver or not. (EDIT: turns out it was the TV--when the TV is actively displaying anything I got high pitched ringing)

- when I fire up the GPUs via furmark, the thumping/rurring noise is still there, but much quieter.

- .firing up the CPUs has no effect on the noise with everything on the same circuit

for now I'm back to the original setup, and just suffering through it... I don't know what to try next... frown.gif
It seems odd to me that the pre-amp output volume has no effect on the sound. I mean if I crank the volume way way up, I'll get noticable hiss, but the normal hiss, not this annoying high pitched weird variable stuff.


EDIT: So frustrating... if I close all the open programs on my PC, the noise goes way down. If I have chrome or media monkey open, variable high pitched whine... I'm baffled
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post #10 of 31 Old 01-14-2013, 11:25 PM - Thread Starter
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Couple more things:

- when I am near my computer (its on the other side of the room), I can hear variable high pitched noises similar to what ends up coming through the speakers. It may be one of the fans, not sure. (Though that can't be the whole story, given that the noise goes away when no significant programs are open, comes when I open most programs, but goes away if I fully load the CPUs... unless its the CPU fan)

- I am currently connecting from my receiver to my amp via RCA cables. My receiver only has RCA outputs, but if I got an rca->xlr cable and used the XLR inputs on my amp, could that help? EDIT: I found a couple rca->xlr I had lying around that I had forgotten about. It helps a little, but can still hear the whine from my listening position. Loading my GPUs doesn't sound so crappy anymore though (need to get close to the speaker to hear the weird noise they make, instead of being clearly audible from the listening position). Still not what I'd like to get it to though.

- I could try a ground loop isolator for RCA, but I have read that they can noticeably degrade the sound
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post #11 of 31 Old 01-15-2013, 04:29 AM
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Any chance you can try a different power supply in the PC? I had something like this a while back and it turned out to be the PSU and bad grounds in that.
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post #12 of 31 Old 01-15-2013, 07:24 AM
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My receiver only has RCA outputs, but if I got an rca->xlr cable and used the XLR inputs on my amp, could that help?

No, it's still an unbalanced connection.
You don't have a ground loop, you have a poorly filtered power supply, try another one.
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post #13 of 31 Old 01-15-2013, 08:11 AM
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Also may be the motherboard. Some are better shielded than others.

Have you tried running your speakers from the receiver?

The fact that it goes away when the cpu is loaded reminds me of info I found when troubleshooting some time ago. Some suggested turning off Cool 'n Quiet (or whatever the intel version is).
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post #14 of 31 Old 01-15-2013, 10:00 AM - Thread Starter
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Quote:
Originally Posted by SAM64 View Post

No, it's still an unbalanced connection.
You don't have a ground loop, you have a poorly filtered power supply, try another one.

And yet, there is a definitely noticeable difference... Not in normal use (where i think there is a diff., but could be in my head), but the loaded gpu sound is MUCH softer with the rca->xlr cables.

Maybe the higher input impedence on the balanced input path in my amp is responsible?

My PSU is a seasonic x-750
The MB is an Asus p6x58d-e


I am wondering about ground loop isolation again... If I cross my mains at 60 or 80, and run audyssey, would I have issues? I've read that its the low frequencies that suffer with a gli.

They don't seem expensive...

Would balanced connections fix this issue?

Of so, a more expensive option would be to move to a preamp with balanced outputs... I'd upgrade my amp to 7 channels (wyred 4 sound 3 channel right now, they offer upgrade to add more channels at whatever he price diff is between the units). I'd probably go with a pre with audyssey xt32 (e.g, integra 80.3).

Alternatively, if there is a good DAC with xt32, I could use that and connect to any preamp with balanced outs.


I'd rather stay away from trying to fix this on the PC end: I tend to replace my computer every 2-3 years, and if I have to go through purchasing and trying multiple MBs and PSUs, that would be annoying. I will look for a bios option to turn off any sort of "quiet" CPU mode when idle.
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post #15 of 31 Old 01-15-2013, 10:12 AM
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This is an extreme measure, but.... smile.gif

Take a long enough piece of wire (typical 18 gauge pc wire is enough) and crimp on spade or ring connectors on both ends. Connect one end to a case screw on the PC side and one end to a case screw on the 4311.

See if that helps. (It won't hurt anything)
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post #16 of 31 Old 01-15-2013, 10:17 AM
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Maybe the higher input impedence on the balanced input path in my amp is responsible?

Does it have a higher impedance? If so, I'd expect there to be more noise...due to the higher input impedance.

Since you've convinced yourself this is a ground loop, best of luck in eliminating it.
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post #17 of 31 Old 01-15-2013, 10:22 AM - Thread Starter
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Hmm, I'll give that a shot.

Another note: I never had an issue when using speakers only powered by the denon. Don't know why...
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post #18 of 31 Old 01-15-2013, 12:13 PM
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Quote:
Originally Posted by SAM64 View Post

Does it have a higher impedance? If so, I'd expect there to be more noise...due to the higher input impedance.

If it does, there's the ground loop. You have to match the impedence on all powered devices on a circuit otherwise you'll be amplifying ground noise from the lower impedance connections.

As a general rule, you'd want all devices that are connected in the audio system on the same circuit and grounded the same.

However, with a PC and all it's peripherals, this becomes an issue. Got a printer? (I know you do as you mentioned above) Ok, that has a PSU as well. Guess what? You connected it to the PC via USB. Now there's another electrical connection where ground loops can be caused?

Got a monitor? Guess what? DVI & HDMI carries ground to the PC too...

You see where I'm going with this...

I'd start by unplugging and disconnecting EVERYTHING from your PC. Then connect only the HTPC, receiver, amp and either a monitor or tv (all on same UPS) and see where that gets you. Also, is your UPS a pure-sine wave unit? If not, this can also cause issues with PCs with Active Power Factor correction, so if you're not sure, just use a standard power strip. Removing any other devices from the entire circuit (all the way back to the breaker) would be a good idea too.

The idea is to break your system down to the barest essentials to see if the problem persists there and then you know where to look for any potential issues.

My guess is the RCA's from the preamp to the amp are carrying a ground loop through to the amp from somewhere in your PC...but I'm not an audio or electrical engineer, so I could be full of B$.

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post #19 of 31 Old 01-15-2013, 01:00 PM - Thread Starter
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Quote:
Originally Posted by SAM64 View Post

Does it have a higher impedance? If so, I'd expect there to be more noise...due to the higher input impedance.

Since you've convinced yourself this is a ground loop, best of luck in eliminating it.

Oops, I was thinking of another amp I had been considering. Turns out this one has the same impedance for both balanced & unbalanced.

I haven't convinced myself of anything... I just don't know much about eliminating noise.

I take it then that the possible solutions I listed in post 14 would only solve a ground loop issue, and not some other issue? (Such as noise from the PC PSU/MB/etc? Those aren't ground loop issues?)

I already stripped my PC down to:
- my 30" monitor (which I powered off, but could bother disconnecting if I do this test again)
- the power cord, which I had going into a power strip plugged into an outlet on circuit 2. (can't reach any outlet for circuit 2 without a strip)
- the mini-HDMI to HDMI cable from my video card to the receiver

As mentioned, the noise was still there. In fact, with the PC, preamp, and amp on the same circuit, the noise was much worse. (The HDTV on the same power strip as the amp was causing noise, but this goes away when the amp is on a different circuit... didn't try the amp in another outlet of the same circuit)


I don't see how this could be an external component issue (outside of the PC), given that the noise changes (significantly) as things inside the PC change--when I load the CPU, load the GPU, unload the CPU, mildly load the CPU, etc.


What I asked (perhaps my intent wasn't clear) is: are there any reasonable solutions that don't involve changing something about the PC? (E.g., would a balanced to balanced pre-amp -> amp connection eliminate this noise? What about a ground loop isolator between the pre & the amp? Etc)

As mentioned above, I'd rather avoid changing the PC--doing so would require:
- ordering a new MB, installing it (which is a PITA), and then seeing if it works...
- ordering a new PSU, installing it (which is a PITA, but not nearly as much as the motherboard), and then seeing if it works.
- if one of the above works, I'm good until my next PC... at which point I order the parts, put it together, and if things aren't ok, spend more money and time installing different parts to see if they work instead.


So, any thoughts on whether a GLI or a balanced->balanced connection (i.e., new preamp) would eliminate (well, massively reduce) this noise?
I suppose I could just give a GLI a shot, as they aren't expensive...
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post #20 of 31 Old 01-15-2013, 01:10 PM
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If it does, there's the ground loop. You have to match the impedence on all powered devices on a circuit otherwise you'll be amplifying ground noise from the lower impedance connections.

Uh, no...we haven't matched impedances in audio circuits since the 60's.
Google impedance, I don't think you know what it means.
Quote:
You see where I'm going with this...

Yes, you've heard of a ground loop, so this must be it....but you don't know about all the other high frequency noise generated by SMPS or other high current digital components, so you're ignoring it.

Quote:
but I'm not an audio or electrical engineer, so I could be full of B$.

that explains it, you should have put that at the beginning of your post wink.gif
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post #21 of 31 Old 01-15-2013, 01:46 PM
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In fact, with the PC, preamp, and amp on the same circuit, the noise was much worse.

If you don't find the root cause of the problem, changing ANY components isn't going to help.

Take the PC out of the equation. Hook an iPod or a cheap DVD player to the Denon. Do you still have noise?
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post #22 of 31 Old 01-15-2013, 02:00 PM - Thread Starter
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Kapone--as mentioned earlier in the thread, if I disconnect the PC's HDMI cable from my receiver, the noise goes away (with the receiver on circuit 2, amp on circuit 1... there is still mild hiss, but none of the variable noise & high pitched whine that come through when the PC is plugged in to the receiver).

With amp & receiver on the same circuit (in same power strip with the HDTV), the HDTV causes noise even with the PC disconnected, but does not do so when the amp is on a separate circuit.
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post #23 of 31 Old 01-15-2013, 02:10 PM
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Whoops...my bad. I missed that part.

However, this statement:
Quote:
if I disconnect the PC's HDMI cable from my receiver, the noise goes away (with the receiver on circuit 2, amp on circuit 1... there is still mild hiss, but none of the variable noise & high pitched whine that come through when the PC is plugged in to the receiver)

and
Quote:
the HDTV causes noise even with the PC disconnected, but does not do so when the amp is on a separate circuit

makes me think, the amp itself may be the problem (potentially).

- Assuming NOTHING is connected to the amp, is there a hiss in the speakers?
- Connect an iPod directly to the amp. Is there a hiss?
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post #24 of 31 Old 01-15-2013, 02:17 PM - Thread Starter
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I have tried disconnecting everything from the amp (aside from the speaker wires and power cable, of course), and there is no hiss. (Well, very very faint)
Its no different when I put the preamp back into the amp.

I have various other things connected to the amp via the preamp, and its all fine without the PC connected.
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post #25 of 31 Old 01-15-2013, 02:21 PM
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General rule of thumb: Check your coax lines and anything that has a 3 prong plug.

This may sound silly but try unplugging your PS3 (don't just turn the power supply off).

Sometimes it is easier to think of things like this; every noise has a source, a path, and a receiver. Source is what you are looking for, path is your tangled mess of wires and components, and a receiver is what is showing the noise.

My situation that I recently remedied (notice I didn't say solved):

Had an old laptop I was using as a HTPC, hooked up to my TV via VGA cable/3.5 mm audio jack. It would display rolling bars of static on the screen anytime the processor was in use and horrible static out the speakers. I discovered that when I disconnected the laptop power supply that the issue went away (laptop was running off battery). Also, the problem became noticably better when I unplugged my PS3. There was still a slight noise in the setup, but much more tolerable. The source of my problem is my antenna coax line.

I remedied the situation when I built my new HTPC as the connection is now HDMI. I changed the PATH of the ground loop.

To solve my problem, I need to properly ground my antenna coax line with my house.

For my setup:
SOURCE = antenna coax
PATH = Antenna Coax -> HD Homerun -> Ethernet Switch -> Laptop -> VGA cable
RECEIVER = PS3 and Laptop

Also, if you google "PS3 ground loop" you will find many people complaining that the PS3 for some reason amplifies a ground loop.

Oh, and I am an engineer (not electrical, mechanical).
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post #26 of 31 Old 01-15-2013, 02:23 PM
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Is your motherboard and PSU "grounded" inside the PC case? I know it's a dumb question, but I have seen weird things. Are the motherboard standoffs metal and so are the motherboard screws? Is the PSU physically touching the chassis and/or screwed in using metal screws?

I'm reaching for straws here...redface.gif
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post #27 of 31 Old 01-15-2013, 02:27 PM - Thread Starter
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I'm not at home right now, but I do know the MB standoffs & screws are metal, and though I haven't messed with my PSU in the ~3 years since I installed it, my recollection is that it is directly touching the chassis. I do know that metal screws passing through the back of the chassis help hold the PSU in place.
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post #28 of 31 Old 01-16-2013, 04:08 AM
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Is your motherboard and PSU "grounded" inside the PC case?

Hope so...it wouldn't work without a return path.
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post #29 of 31 Old 01-16-2013, 10:56 AM
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Quote:
Originally Posted by SAM64 View Post

Uh, no...we haven't matched impedances in audio circuits since the 60's.
Google impedance, I don't think you know what it means.
Yes, you've heard of a ground loop, so this must be it....but you don't know about all the other high frequency noise generated by SMPS or other high current digital components, so you're ignoring it.
that explains it, you should have put that at the beginning of your post wink.gif

Sure...

I'm very familiar with impedance, EMI and all sorts of audio noise sources. I've been building PCs professionally since the early 90s (well before I joined AVS) and have installed countless systems in HTPC applications. But you're assuming the source of the issues is EMI and not the whole system en totale. As for impedance matching vs bridging...I know what your saying, but I also know that it's still an issue for mixed sources today, especially when PC's are involved.

I'm sure you weren't really trying to be derogatory in your comments, so I'll move along and try to address the OPs problem.

The problem with ground-loops is that not all "grounded" circuits are grounded well.

EMI plays a role, and based on the OP's comments about the noise changing under different scenarios, can definitely be worth looking into. However, I understood the issue to be that the OP didn't WANT to replace components and was looking to minimise the effect without it. You can't really get rid of the EMI inside of a PC without replacing components (there are professional-grade soundcards that are heavily shielded to help with this). I've also heard of bad HDMI cables and connectors causing huge issues with noise artifacts (hums, hissing, etc). So changing cables/connectors/inputs might be worth a shot too.

One of the best primers on this topic I've ever found is this document. It's full of lots of good stuff to understand the issues being faced.

Some of the other posters have mentioned unplugging other devices as well. That's because poor quality PSUs (perhaps including the one inside your PC) "dirty up" the power lines by returning power that doesn't have a 60hz frequency or induces some kind of harmonics/sag/etc that produces a less than perfect source to another component down the line (or back to the grid). Years (and years) ago, I personally found a huge issue with an old CRT monitor that was causing a BAD hum on a digital coaxial connection. Unplugging the CRT, made the hum go away. I had to replace the monitor to remove the issue, which is too bad as it was a really nice Samsung Syncmaster model. There is a reason that companies sell high-end power conditioners. The point is that there are many things that can cause a problem down the path.

Can you hook up the PC via RCA (use 3.5mm to RCA adapter) to the AMP directly and see if that has any issues? Perhaps, does your system have another digital connection (TOSLINK or SPDIF coax) to connect to the preamp and see if you can isolate the input issues?

For your PC silencing needs...check out www.silentpcreview.com

For your WHS needs...check out www.wegotserved.co.uk
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post #30 of 31 Old 01-16-2013, 11:50 AM
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...I know what your saying, but I also know that it's still an issue for mixed sources today, especially when PC's are involved.

Sorry, you're still incorrect on that one...it's a problem that was solvede decades ago.
Quote:
I'm sure you weren't really trying to be derogatory in your comments, so I'll move along and try to address the OPs problem.

I'm sure you werent either, it just came across that way.
Quote:
(there are professional-grade soundcards that are heavily shielded to help with this)

can you name one or two?
Quote:
That's because poor quality PSUs (perhaps including the one inside your PC) "dirty up" the power lines by returning power that doesn't have a 60hz frequency or induces some kind of harmonics/sag/etc that produces a less than perfect source to another component down the line (or back to the grid).

You mentioned you werent an EE....this is clear, don't try to explain things you clearly don't understand.
Quote:
There is a reason that companies sell high-end power conditioners

yes, to extract money from people who don't understand electronics.
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