i7 PC electrical noise leaking into audio recordings

[skb_oc3d]

Hello,

I have a very challenging and annoying electrical noise problem that I believe is traceable to either my PC's power supply, motherboard, or processor. I hope some knowledgeable and helpful experts out there can help me figure out what to do next. Unfortunately, I don't have other power supplies, motherboards, or unlimited funds to drop and swap until the noise is gone. I need to carefully consider my best option(s) and go one step at a time. Here's the story:

Last month I built a new Intel i7 PC for music composition and audio recording. Everything was going great until I tried recording line-level analog audio from my hardware synthesizers. My i7 PC has an M-Audio Delta 1010 sound card (external A/D converter box) that was previously used in a Pentium III PC and made pristine recordings in that role. To my horror, analog recordings into this new i7 PC are accompanied by an obnoxious, wide-spectrum buzzing noise centered near 2.5kHz. This electrical noise is very obviously audible in .wav files recorded on this i7 PC.

Fortunately, I was able to reduce the noise by 8dB by disabling Speedstep in my bios as noted in a thread on the Corsair forum (ironically, thoese people cite acoustic noise whereas this solution helped reduce my electrical/audio noise). After this solution, however, the noise is still audible and needs further reduction/elimination for these recordings to be up to par.

A further solution is having my Delta 1010 A/D breakout box powered by a rackmount Furman power conditioner (RP-8). Supposedly these units have AC filtering circuitry within, and sure enough, placing this unit between the A/D box and the AC wall plug reduced the recorded electrical noise by another 2dB. But that's still not good enough - it's still audible, albeit at a low level.

So I have a few older PCs that have been reliable for pristine audio recordings for many years - one of which is a humble Toshiba 1.4GHz Pentium M laptop with an RME Hammerfall PCMCIA sound card (Multiface external A/D box). I repeated these recording tests using this old laptop with the following two conditions: new i7 powered OFF and i7 PC powered ON.

With the i7 PC merely powered ON (keep in mind, there are no connections between these 2 PCs.. and the synthesizer is being recorded directly into the Hammerfall A/D inputs.. so the only common link is that they both are drawing AC power..), the laptop records the SAME ELECTRICAL NOISE as originally found/noted in the i7 recordings (at a slightly lower level)!

With the i7 PC powered off, however, the laptop audio recordings were pristine as expected - no noise whatsover. Therefore, this electrical noise is making its way from the i7 PC and into my other audio gear via my home's AC power path.

My question for the experts that know PCs, power supplies, motherboards, and AC: how should I go about eliminating this noise? What's my next best step?

(FWIW, Antec customer support recommended that I update my motherboard bios, which I promptly did, and found no improvement/change in my recording tests).

If the root cause is the i7 CPU, would switching to a different CPU be the best solution? For example, would I find solace in an Intel Core 2 Quad or AMD Phenom II CPU?

Or, is it the Gigabyte motherboard that needs to be swapped out? Isn't it the motherboard's job to filter and control the emissions of noisy chips? But isn't Gigabyte well-known as the best motherboard manufacturer out there? What could I try that would make a difference - Asus? Foxconn?

Or, is the PC power supply at fault? If I simply bought a much more expensive power supply, would I also buy better DC -> AC filtering? Is there a specific power supply model out there designed to handle the i7 and keep its noise within the PC?

Sorry for the long post, but there is a bit to consider. Your thoughts, comments, and questions would be most welcome. Here are my PC specs:

CPU: Intel i7 920 2.6 GHz

Motherboard: Gigabyte GA-EX58-UD4P

RAM: Super Talent 6GB DDR3

GPU: Sapphire Radeon HD4770

HD: Western Digital WD10000LSRTL

DVD: Sony AD-7240S-0B

PS: Antec Earthwatts 430W

Case: Antec Sonata Elite

Sound: M-Audio Delta 1010

Thanks,

Scott

 

[mayhem]

contra to popular belief some mother boards are not that well made and noise does leak through on some high end recording systems.

Ive seen some thing very similar before in the past and it took a long time to fix the problem.

We ended up swapping out the PSU for a better and more stable one because we eventually found this to be the cause.

How ever this may not be your answer as there are many components and simple things like unshielded wiring can have a adverse effect on the way sound can flow through the system.

Personally i would first check all the cable's are moved and try to clean up with in the system to see if this has any effect.

Secondly i would ask and borrorw a mates PC power supply or even take it down to a shop and ask if they could try one out in the system. to see if this is the route cause.

If after all that and you are still having a problem. It may be some thing like the mother board may be slightly out of sink in the case and some how some noise (or electrical signal) is interfering with in the system it self.

Another option is to disable the on board sound and get a decent sound card that way you are eliminating any interference that the motherboard could be making.

i very much doubt the i7 has this effect over a audio system what so ever.

 

[Rastalovich]

I'd be tempted to try and shield the M-Audio 1010 card, and/or change the pci slot if it helps distance it. Or if it's the proximity of the PSU - shield that.

The noise source tho could be a handful of things that u would have to deduce from a process of elimination.

If it's just a workstation, u may consider putting a weaker gfxcard in there. I found them to emit quite a bit. Find something that's silly-cheap, I mean u can get £10 pcie cards if u look long enough - they'll just display.

 

[skb_oc3d]

Hi Mayhem,

Thanks. Which PSU did you use to solve your noise problem?

Hi Rastalovich,

How would I shield the Delta 1010 PCI card? The Delta 1010 A/D converters are mounted in an external rackmountable breakout box (which has its own AC/DC power supply) to avoid noise issues like this. The audio inputs are digitized at the breakout box and are sent as data via a parallel cable to the PCI card. Since the noise is leaking into the recorded audio, doesn't this mean the noise transfer is occurring within the breakout box (not within the PC case)? Or are you suggesting the electrical noise is making its way from the Delta 1010 PCI card, down the parallel cable, and into the breakout box?

Thanks,

Scott

 

[skb_oc3d]

Results

Just wanted to write back and say thanks for all of your help and suggestions!

My initial nasty -70 dB Delta 1010 noise floor is now -84 to -86 dB. The Delta 1010 still has a dB or two of pitched AC noise riding on DC, whereas the RME (still on the Pentium M laptop...) has negligible noise on its DC around -89dB.

Another significant related finding is that analog output #1 of the Delta 1010 is MUCH more noisy (+15dB) than outputs 2-8. The DC power input happens to be right next to output #1...

Here is a summary of my initial efforts:

- relocated i7 AC cable from the same power strip as the Delta 1010 to an "upstream" path closer to the AC plug. result: at least 1 dB electrical noise reduction.

- added Furman power conditioner between Delta 1010 AD box DC adapter and AC outlet. result: 1-2 dB electrical noise reduction.

- disabled C1E and E1ST ("speedstep") parameters in the Gigabyte EX58-UD4P bios. result: 6-7 dB electrical noise reduction.

and my follow up efforts:

- disabled Delta 1010 MIDI out driver in Sonar. result: 5-6 dB electrical noise reduction.

- disabled Sonar's recording metronome audio output. result: ~1 dB electrical noise reduction.

- swapped Antec Earthwatts 430 PSU for BFG GS-550. this effected the frequency components of the AC noise (i.e. normalized AC noise "sounds" somewhat different), but did not effect the electrical noise amplitude.

- physically routed the Delta 1010 parallel cable and AD converter box to a new isolated location in the room. also tried moving power, source analog, and data cables around while recording. no effect on electrical noise.

- strip down the PC down one component at a time. decided not to do this because the Delta 1010 AD converters are disabled prior to Windows XP loading the M-Audio drivers. therefore, any measurements of Delta 1010 performance with the PC in bios (or DOS) would be unrealistic and misleading.

- disconnect DC case fans. decided not to do this because this is an unrealistic and possibly unsafe operating condition.

In summary, it was primarily the combination of the Gigabyte bios "speedstep" settings and Delta 1010 MIDI output that made up the majority of the recorded electrical noise. Among my recording equipment, this electrical noise is unique to my new i7 PC and concerns me because I have to be careful about dynamics processing applied to audio recorded through its analog inputs.

Someone on Anandtech suggested that the Gigabyte EX58 i7 motherboards create an audible whining/buzzing noise. It is possible - although unproven - that the source of that problem also causes the electrical noise I experienced. Personally, I would suggest that anyone who needs professional quality audio recording to be careful when choosing a motherboard and consider the issues presented in this thread and elsewhere. Good luck.

Thanks,

Scott

 

[mayhem]

well done all though most of that noise went above my head.

Im supprised Noise is crated from the MB wich is good find really and ill add that to a list of thing to keep an eye for..

 

[Rastalovich]

In terms of the shielding of the card, it would involve having some kind of hood that u would need to diy to cover the card - surface atleast.

Within our recording areas, and the office areas, we mainly use radioman cards that come with a posted pcb-type shield on them.