pro audio "whine" [SOLVED]

[homesnake]

Hey everyone,

I have managed to build a really nice rig with everyones help here, unfortunately I have recently discovered a flaw that makes it somewhat unusable for pro audio.

The issue is an audible high pitched "whine" coming from inside the case whenever an audio app (ANY audio app) is launched. launching an audio app triggers the noise. I have an external firewire audio interface and a USB interface, which both suffer from the issue.

It's a known issue which was known to affect mac pro 2009 tower models. The issue is fairly well documented here:

http://macproaudiobug.byethost31.com/

and here:

http://forums.macrumors.com/showthread.php?t=866341

(if you are curious as to what this sounds like, download the attachment "signal on audio jack output.m4a.zip" at the bottom of the first post)

Apple has a fix here:

http://support.apple.com/kb/DL1042

Which I tried (yes I do know I am not supposed to install Mac hardware specific updates, but I'm kind of desperate). Of course it failed to resolve the issue.

I was surprised that my Hack would be prone to this issue...

Other people with real mac pros have avoided installing Snow or rolled back to Leopard to avoid the issue, so it seems not to be a hardware issue, this much I have figured out.

I read somewhere (if memory serves) that a person involved in the hackintosh scene discovered the source of the issue was a power management issue. Could this be the case? Could a possible fix be rebuilding the hack as a non DSDT machine?

Any advice appreciated.

Please don't say "stick it in the closet" lol

 

[Lnx2Mac]

Re: pro audio "whine" - apple audio update fix not working

homesnake,

This might be somehow related to the nvidia/intel squealing issue many reported on the net...

On my setup (though without FW audio), I could sometimes hear this high-pitch noise with opengl screensavers... cakemonster and others have reported issues with 3d software.

Some workarounds you might try...
1) I found that updating the BIOS to F9 almost completely fixed the issue (had to open the case to make sure, as it seems the noise dampening of my case was filtering most of it).
2) Some found that setting the VCore to a fixed value solved this issue.
3) Disabling C1E might be helpful too.

Good Luck, and please post back your results !
Lnx2Mac

 

[Guv]

 

[Lnx2Mac]

Re: pro audio "whine" - apple audio update fix not working

What BIOS are you using?

See my sig... F9

 

[Guv]

 

[homesnake]

Re: pro audio "whine" - apple audio update fix not working

BIOS is relatively new if not the latest, unfortunately I'm at work, I'll check when I get home.

Lnx2mac is there a BIOS you could recommend, or conversely are there any to avoid?

I'll try out all your suggestions and report my findings tonight.

 

[humph]

Re: pro audio "whine" - apple audio update fix not working

I dont recall having this issue (on 10.6.3) with my config.
(But due to excessive case fans, I would not hear any whine unless it was fiarly loud!)
Used MOTO Traveller via Firewire and DP5.13/CueMixFX etc.
But my MB etc is not the same as you have, so that's one difference.

Also using the iMac11,1 SMBIOS, wonder if you have that also, or use MacPro?
Perhaps there's something going on there?

I did have the PSU whine until followed Lnx2Mac's suggestion to set a fixed VCore.

 

[homesnake]

Re: pro audio "whine" - apple audio update fix not working

I am running Mac11,1 SMBIOS for sure, that I know. Very curious now if maybe it is the PSU whine you mention.

Forgive my newbness but how would set a fixed Vcore? does this mean speedstep is disabled in part? Is this set just a setting in the BIOS?

I would trade any power/heat savings gladly to eliminate this issue, speedstep be damned!

I wish I wasn't at work... a few hours to go.

EDIT: just to try and give a better description of the noise, if you aren't paying attention one might easily assume that the noise is fan or disk related, or as you mentioned if you have other noisier components it would be drown out. I am positive it is the issue described in the first threads after I listened to the mp3 provided on the macrumors forum thread- it is a highly pitched yet not overly loud noise, the only way I can describe it is as a metallic oscillating whistle, triggered by ANY audio app being launched.

 

[homesnake]

Re: pro audio "whine" - apple audio update fix not working

interesting. I'll tweak the BIOS etc first as per the previous posts and if that doesn't help I do have a new power supply that I can swap in and see what happens.

 

[Lnx2Mac]

Re: pro audio "whine" - apple audio update fix not working

BIOS is relatively new if not the latest, unfortunately I'm at work, I'll check when I get home.

Lnx2mac is there a BIOS you could recommend, or conversely are there any to avoid?

Get the F9... it's safe to use.

Forgive my newbness but how would set a fixed Vcore? does this mean speedstep is disabled in part? Is this set just a setting in the BIOS?

Yes, in the "Advanced Voltage Settings" page.

I'll try out all your suggestions and report my findings tonight.

Please report back.