Interference noise on home-built PC

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antoniosk

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#161901 22-Jan-2015 20:13

Recently I rebuilt my PC - bitfenix Merc Alpha case, gigabyte GA-F2A75M board, AMD A5800 chip and pretty standard DVD-Writer.

There is interference noise bleeding into the sound.

Regardless of whether I use front or read 3.5" sound out, or sound out via a USB dongle, there is noise.

I've relocated the transceiver from the wireless keyboard (Logitech variety), and that's made little or no difference.

The power supply is new but no-name brand.

So I'm left wondering where's the next step? it bugs me to hear it.

________

Antoniosk

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#1220375 22-Jan-2015 20:55

Unfortunately not all motherboards have a good design as far as on-board sound. It's unbalanced, not shielded, if it doesn't buzz and hiss a little I'd be out right amazed.

Try changing the PSU, and make sure every place on the motherboard a screw is meant to be grounded to the chassis is in place. Chances are though it's a cheap on-board line amplifier situated near a lot of noisy signally on the motherboard and completely unshielded.

Short of that, start looking at a PCI or PCIe sound card etc... Stay away from anything to do with Creative cards. They are mostly hardware fixed at 48KHz multiples (you can tell by multiplying the crystal frequency if it supports hardware 44.1 or on the fly software re-sampling to and from 48KHz etc...). A decent card will have another crystal that supports multiples up to 44.1Khz for CD playback etc..., proper hardware support, not DSP re-sampling on the fly.

Anything not on-board is a step up though.

I do studio work so I use ASI5111's which cost about 3-4 motherboards worth. But they are dead silent and if you see how professional cards are shielded then look at a motherboard chipset.... you can see why they buzz. Especially if anything noisy RF wise nearby.

richms

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#1220379 22-Jan-2015 21:02

if you have optical out - http://www.aliexpress.com/item/SMSL-SD-793II-DIR9001-PCM1793-OPA2134-Coax-Optical-MINI-DAC-Headphone-Amp-EG246/1690436505.html

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gzt

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#1220396 22-Jan-2015 21:23

Do you have or can borrow another power supply for comparison? That is easy.

Maybe post the system spec. Btw if mb is faulty it will be replaced under warranty for this issue.

antoniosk

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#1220439 22-Jan-2015 22:50

gzt: Do you have or can borrow another power supply for comparison? That is easy.

Maybe post the system spec. Btw if mb is faulty it will be replaced under warranty for this issue.

Cooler master elite 400w
Gigabyte Ga-f2a75m-d3h
Amd a5800
Kingston HyperX KHX1600C9D3K2/8GX ram (2x4gb)
And the bitfenix merc alpha case

One thing I've noticed is the power supply is at the bottom, and the motherboard connectors for the front panel (usb ports + sound) is directly above them. The power cables traverse the board connectors.... If the mercs wire shielding is average... Maybe some bleed from somewhere?

________

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kiwirock

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#1220445 22-Jan-2015 23:16

antoniosk:
gzt: Do you have or can borrow another power supply for comparison? That is easy.

Maybe post the system spec. Btw if mb is faulty it will be replaced under warranty for this issue.

Cooler master elite 400w
Gigabyte Ga-f2a75m-d3h
Amd a5800
Kingston HyperX KHX1600C9D3K2/8GX ram (2x4gb)
And the bitfenix merc alpha case

One thing I've noticed is the power supply is at the bottom, and the motherboard connectors for the front panel (usb ports + sound) is directly above them. The power cables traverse the board connectors.... If the mercs wire shielding is average... Maybe some bleed from somewhere?

When you say interference noise, is it like white noise (static), a crackly sound like a bad cap or resistor on the audio output, or a mains hum? A mains hum is common if there's any other equipment connected to a different earth potential. Consumer grade equipment especially PC's are very prone to mains hum when connecting various equipment together outside of the PC etc...

The audio connector on the motherboard won't be shielded, and I doubt the line amp section so try to keep any power cables as far as possible from it. Also try not to use the spare slot closest to the audio chipset to see if it makes a difference (I'm guessing you're not though).

Is it a sound setup that can detect between headphones and line level devices connected? You could try making sure if there's the configuration option to make sure it's not set to amplify or auto-detect between types of devices connected.

I'd first try to assess if it's a mains hum or not caused by an earth-loop.

edit:If you have a spare CPU fan floating around, try and disable the current CPU fan and try another cooling source in-case it's EMI from the CPU or any case fans. Probably not but it's possible.

gzt

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#1220454 23-Jan-2015 00:23

Good points above. Try running the power supply outside the case if that can show better cable routing and position.

antoniosk

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#1324985 15-Jun-2015 14:03

Ok i'm coming back to this as its still annoying me.

Before I jump into the case and start changing wires, a small video for folk to give a listen to and possibly offer some learned thoughts:

https://youtu.be/YNeo4q1XldA

Grunt...

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Jase2985

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#1324988 15-Jun-2015 14:09

an error occurred with the video

ubergeeknz

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#1324989 15-Jun-2015 14:10

Unplug everything else which is on the same circuit, and see if the problem goes away. Also turn off lights etc. Hell, turn off everything except the PC.

antoniosk

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#1324990 15-Jun-2015 14:12

ubergeeknz: Unplug everything else which is on the same circuit, and see if the problem goes away. Also turn off lights etc. Hell, turn off everything except the PC.

Doesn't make a difference... happens in 2 different houses with the just the PC running on the one plug (no fridge either)

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ubergeeknz

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#1325003 15-Jun-2015 14:18

antoniosk:
ubergeeknz: Unplug everything else which is on the same circuit, and see if the problem goes away. Also turn off lights etc. Hell, turn off everything except the PC.

Doesn't make a difference... happens in 2 different houses with the just the PC running on the one plug (no fridge either)

Ugly. Try a different PSU. Don't know if I'd run it outside the case, as then your case will be ungrounded, but you could try it if you want. The PSU is in a metal box, so I doubt PSU shielding is going to be the problem.

antoniosk

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#1325017 15-Jun-2015 14:35

ubergeeknz:
antoniosk:
ubergeeknz: Unplug everything else which is on the same circuit, and see if the problem goes away. Also turn off lights etc. Hell, turn off everything except the PC.

Doesn't make a difference... happens in 2 different houses with the just the PC running on the one plug (no fridge either)

Ugly. Try a different PSU. Don't know if I'd run it outside the case, as then your case will be ungrounded, but you could try it if you want. The PSU is in a metal box, so I doubt PSU shielding is going to be the problem.

I suspected that.... cooler master PSU as well. Guess I'm opening the case in the weekend...

________

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richms

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#1325186 15-Jun-2015 16:28

Just heard normal poor quality PC audio noises on that video.

Doesnt help with unshielded plastic speakers like that either.

Richard rich.ms

antoniosk

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#1325196 15-Jun-2015 16:38

richms: Just heard normal poor quality PC audio noises on that video.

Doesnt help with unshielded plastic speakers like that either.

Thanks Rich

Noise occurs on monitor speakers, quality stereo and headphones too, from the audio ports (front and back). Also happens when I plug a USB sound bud in too - which makes me think it's a wider issue somewhere.

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richms

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#1325204 15-Jun-2015 16:47

Cheap speakers will demodulate a lot of the RF crap on the power and audio lines down to something you can hear.

USB devices should be a lot better, so long as you didnt get something cheap and nasty. But even some of the "premium" ones don't adequately condition the power.

No power supply will be clean enough for audio devices when it has several massively high current stepdown converters for the CPU and GPU running off the same power supply. Most USB audio devices slap a couple of capacitors across the power and call it done.

If you buy a piece of crap like this http://www.pbtech.co.nz/index.php?z=p&p=SEVOEM8599 then I would expect it to be worse than typical onboard quality. That same device is about $2-3 on ebay etc.

There are some nice affordable soundcards and external devices from asus. They tend to be a good middle of the range device that is pretty damn quiet on the output.

The other issue is how you are powering those speakers? If its a USB powered speaker like I have seen many of on ebay etc then you have a groundloop happening. Try it off a USB powerbank so it isnt looped back to the PC and see what it does. But not holding breath.

Richard rich.ms

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