Fixes for hard drive noise creeping into audio signal?

[atavacron]

I'm using a hackintosh here at the studio. I find that regardless of whether my RME interfaces are plugged in to my console or not, the computer is somehow leaking crappy digital artifacts into...get this...the main bus of my console. This is not showing up on any of the I/O. The noise is slightly less present when I pull the FireWire cable from my interface, but it's still there.

What the heck? This noise includes all hard drive access, and such trivial things as screen refresh and mouse gestures. If the computer is doing something (anything), it is accompanied by high-midrange clicks, buzzes, whirrs, you name it.

My troubleshooting did include ground-lifting first the computer, then the console. I also tried disconnecting everything but the flatscreen monitors, keyboard and mouse. I plugged the computer into a separate circuit, which is definitely on a whole other 20A breaker than all the control room stuff.

The only thing I can think of to do next is to take the hackintosh out of the rack that functions as system ground. Maybe it's that the case is grounding to the rack? That's true, but I don't see why it would matter. Or should I go hunting for a special power supply (500W ATX) that could provide some sort of fancy filtering?

Sigh.

[atavacron]

This was useful: http://www.soundonsound.com/sos/nov04/a ... oblems.htm ...However, I don't have an internal sound card.

I forgot to mention: the noise doesn't start happening until Mac OS starts booting. The PC side of the boot process is dead silent, and then as soon as the first grey screen comes up, it's like an army of leafcutter ants is going to work on my monitors.

[Nick Sevilla]

I agree. it could be chassis ground. do try to mount it elsewhere, and start testing again.

Cheers

[atavacron]

Thanks Nick

[atavacron]

Still working on this issue...

I've now tried every combination conceivable of plugging the computer into different outlets, lifting the ground, isolating the case from the rack, and finally it occurred to me to disconnect everything - everything - from the machine while running. Guess what? The noise is still showing up on my master buss. This means...RF noise generated by the main drive? Hmm. Well, the chassis of the machine is definitely grounded to the house main ground - I get continuity between the two when tested.

Next trouble shooting step is to (groan) take the machine out of the rack and start increasing its distance from the desk. Or at least the rack. That should give me a starting point for figuring out what's up. I also have an idea to clone the main drive and see if running a different main drive clears up the issue.

All of the 2-track cabling (I have a 2-channel converter, 2-track tape machine, and an auxiliary line input connected to the console's three dedicated 2-track circuits, all feeding into and out of the master section) happens to run directly behind the machine. But ironically none of these signals have the noise on them. Kind of makes sense, since they're all balanced.

More to come, any advice appreciated...

[jhharvest]

It kind of sounds like the dreaded firewire whine that Macs have been suffering of. Would you be able to borrow a firewire card with a different chipset in it for testing?

[atavacron]

Good idea...however I've actually got three ways of deriving FW out of this machine...onboard hardwired, auxiliary onboard, and PCI. All three give me some variation on the noise.

So I did try moving the machine out of the rack. Which worked, actually. I slowly pulled the thing out and you can hear the noise decrease as you go. Though I haven't tried it with the interface attached.

I'm going out on a limb here and I'm going to guess that it's my ASUS EN9600GT graphics card, because when I flip the machine over and put the end with the PCI cards AWAY FROM THE GIANT COIL OF MULTICORE THAT RUNS TO THE CONSOLE, the noise decreases by about 2/3. There's a little bit of documentation online about this card causing similar noise (and even a YouTube video of some gamer demonstrating it). Plus, if it was the hard drive, why would the noise only show up when the Apple OS starts? Wouldn't it show up on boot?

Anyways, I've ordered a piddling little utility graphics card, the ASUS EN210, which has matching overall specs as mine - and is similarly fanless, which is key - but would never be able to handle serious gaming. Lucky I am not a gamer, nor are any of my guest engineers...

Guess we'll see if that fixes it.

[Snarl 12/8]

I slowly pulled the thing out and you can hear the noise decrease as you go.

Dude, I know you were at your wits end troubleshooting, but don't ever move a non-laptop while it's running. I used to do this all the time until I had a hard drive just up and die from a very gentle 3 inch move. It took me a very long time to admit it was the hard drive, because I couldn't fathom how it got damaged. Hard drives blow my mind with what they're capable of these days. But they have very narrow comfort zones.

[trevord]

I only mention this long shot because you seem to have tried everything else
It could be just interference from the screen - older larger monitor screens and unshielded speakers used to make this kind of noise

you can try shielding speakers and increasing distance between screen and speaker

[SafeandSoundMastering]

This could be RF through air (unlikely) or through mains I guess. Might be worth buying some RF filtered mains boards. Try putting your PC ion another ring main (i.e. get an extension and plug it in in another room) Maybe the electronics in your master bus section is faulty and some part of the circuit is acting as an antenna.

Try this... worth having at this low price anyway IMO.

Tacima-Conditioner-Frequency-Interference-Filter

These are not expensive but are pretty decently designed.

SafeandSound Mastering
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