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PC Power supply noise problem with sound cards - need help
PC Power supply noise problem with sound cards - need help
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Old 10th April 2003, 08:43 AM   #11
Cradle22 is offline Cradle22  Germany
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Join Date: Jan 2003
Location: Dortmund, Germany

While generally disliking this device (not supported by kxDriver...), you could try using the Soundblaster Extigy device, since it can be put anywhere, has it's own power supply, no you could exclude any influences from computer internals... Only the digitalized signals get passed through USB to the computer...

If you can try it for free , do so...


A Sacrifice For Freedom
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Old 10th April 2003, 11:48 AM   #12
halcyon is offline halcyon
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Join Date: Apr 2002
Thanks for the tip.

I don't have Extigy and it doesn't do what I want, so it wouldn't solve my issue.

However, I know by looking at other people's measurement graphs that they have been able to get much lower noise figures with the exaxt same model sound cards that I have.

So, it's something in my system or mains electricity (or something else pertaining to my setup) that is causing the problem.

I'm hoping I could find and alleviate/eliminate it rather than keep on switching to inferior sound cards

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Old 10th April 2003, 02:36 PM   #13
carlosfm is offline carlosfm  Portugal
Join Date: Mar 2003
Location: Lisbon, Portugal
Talking waaaaaaaaaaaaaait!!!

I had a similar problem (I suppose), since I changed home.
On my new house I had a humm problem with the sound card that I never had.
Instead of fiddling, you need to think simple first.
If everything is the same (except the house ) why does it hum??!
I noticed it while recording from vinyl, there was a noticeable noise that I never had (with loud music playing it's hard to notice).
Do you know what I did?


Crappy earth, noise for sure.
It's better not to have.
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Old 10th April 2003, 04:26 PM   #14
halcyon is offline halcyon
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Join Date: Apr 2002

you're probably onto something here.

I checked... our building has very old wiring.

Usually it's done with three phase wires, one ground wire and one neutral wire.

In our aparment we only have two phases and no ground wire, so grounding has been done using the neutral wire (perfectly legal to do and recommended for old buildings, done by a professional/certified company it seems).

So, it could be that the problem with the ground (or neutral) is the cause here?

I really need an electricity quality meter now

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Old 10th April 2003, 04:35 PM   #15
ALW is offline ALW  United Kingdom
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Join Date: Jun 2001
Location: UK
Default Try this


Download the trial of Spectralab, and do some FFT fo the sound card o/p for analysis.

A common problem is to leave unused inputs enabled when doing high-quality work. The mic input is often the worst - are you sure the noise is not mixed from other inputs?

Try muting all inputs except the one you're using.

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Old 10th April 2003, 05:39 PM   #16
carlosfm is offline carlosfm  Portugal
Join Date: Mar 2003
Location: Lisbon, Portugal
It's easy to disconnect the earth wire from the plug and try.
I think it's the first thing to do.
You may be surpised, because I can bet the problem is the earth.
It can be good for fridges and washing machines, but not good for audio.
A defective earth is really not good for audio.
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Old 10th April 2003, 06:32 PM   #17
Pjotr is offline Pjotr
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Default Ground loops ?

Ehm Andy, Halcyon did post already some pics of FFT’s. The pics were taken in loop through with nothing connected to the soundcard. That means that there are no ground loops in that case. Still the hum is –80dB FS. That means the hum can only come from inside the PC. I think Halcyon is quite close with his first post: The hum comes from the PSU itself. IMHO it is worth trying another PSU and see if this make any difference. No mains cable running internal along the mainboard, to a frontpanel mains switch for instance?

With my internal M-Audio PCI card the mains hum is well below –120 dB. Here I already did post some pics of the M-Audio card, scroll to the bottom of the page. RME is well known for its excellent audio cards.

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Old 12th April 2003, 02:01 PM   #18
halcyon is offline halcyon
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Join Date: Apr 2002
Ok, update time.

I removed my PC from the mains ground contact for testing.

Then I ran the RMAA 5.0 tests again and the results are almost exactly the same.

So, it seems that the crap grounding wasn't the main cause of the 50 Hz noise.

I have found a decent power supply (in terms of acoustic noise) that I'm going to try out as soon as it's available at local resellers.

I'll report back after that.

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Old 14th April 2003, 01:35 PM   #19
sangram is offline sangram  India
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Location: India
Most of the time the ripple noise in sondcards is due to the mainboard, and sometimes due to the PSU. Remember the CPU is hogging a lot of power, and a mainboard with poor CPU power regulation - essentially from the 5 and 3.3V rails - will be throwing a lot of noise back onto the rails. Please try out one of each the PS and mobo.

Sometimes even the drivers will make a difference. I have an SB Live! installed which has a lot of noise in 98 using the Creative default drivers, and under 2000 with the Kx driver is quiet as a mouse - or as quiet as a Live! can be, which rally isn't all that great, but does my job well enough.
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Old 16th April 2003, 07:28 AM   #20
halcyon is offline halcyon
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Join Date: Apr 2002
More update time:

I don't think it's the drivers in this case, because other people get much better readings with the same card using same drivers. However, I do agree that especially Creative drivers are well known for their ability of mungling the sound (especially due to resampling artifacts).

I got a Fluke Electricity Quality analyzer and a friend who works at an electricity testing lab to hop over.

We quickly tested the ground potential (very close to nominal zero, no constant voltage there), the voltage (very nice sine waveform, below 2% THD, almost constant 235V as it should be) and some other measures.

Of course, some loads on the mains cause the current to break down into ugly waveform (for instance a television does this), but I have the problems even if I don't have these aforementioned devices connected to the same wire.

Haven't yet measured the current waveform for the computer, so I will do that after I've run a bit of logging at my main hifi rig first.

Preliminary testing however suggest that it is not the ground nor the mains electricity that is causing the problem. I'll be hopefully wiser after I've run more tests (and for a longer duration).

I've already ordered a new PSU and will do measurements of the sound card when I get it / have it installed.

More updates to follow, in case anyone's interested

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