Noise through JACK on MacBook

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wesrtx
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Noise through JACK on MacBook

Post by wesrtx »

I recently set up my NI Rig Kontrol 3 with my MacBook 4,1 (running CrunchBang Waldorf) and got some nasty noise (mostly a high-pitched trill, but there's some low frequency content in there as well) coming out of rakarrack and Guitarix into my amp.

I had thought the software itself was just noisy due to settings, but both apps produce the noise independently. So I tried experimenting with different cables, my amp, power connections, etc. but nothing helped. Then I tried unplugging all my audio devices and starting JACK, and noticed I could barely hear a high-pitched ringing sound coming from *inside* my computer.

It appears JACK is triggering something in some onboard device and that's where the noise is coming from. I tried adjusting the settings in Qjackctl, playing with the levels in alsamixer, and killing PulseAudio and various hardware-related processes, but I'm still getting the noise! This never happened recording under OS X with Logic and NI Guitar Rig.

I have read that some Realtek chips (perhaps including the one on the MacBook 4,1's motherboard) can produce this kind of noise (something about the chip's input and output jacks not being properly grounded), but haven't found anything about this particular situation and how to fix it.

Any ideas?

Shadow_7
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Re: Noise through JACK on MacBook

Post by Shadow_7 »

On one of my old laptops, the mic input and headphone output had shared elements. As in I could not multi-track, record something new while playing something old at the same time. Because the something new (input) would have bleed over from the something old (output). Perhaps this is part of what you're getting, a sort of feedback that is independent of the input because it's the output looping back.

If you have the option to NOT run FULL DUPLEX and run playback only, you might get rid of the high pitched noise. As in use -P instead of -D for playback only instead of the full duplex (default?) for jackd. Just a guess.

wesrtx
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Re: Noise through JACK on MacBook

Post by wesrtx »

I gave that a try, but it didn't change anything--I can still hear the onboard noise when I put my ear up to my computer.

I played around with the input and output device options in Qjackctl, and this is what I figured out:
  • If I set both input and output to HDA Intel (uses the onboard Realtek chip), the VU meter in Guitarix shows little noise, which is what I'd like to see.
  • If I set input to HDA Intel and output to RigKontrol3, I get a crackling sound and a very loud high pitched squeal (like feedback) through the amp. This noise even shows up on the Rig Kontrol's output meter.
  • If I set input to RigKontrol3 and output to HDA Intel, I get loud, continuous white noise through the computer's speakers or headphones (whichever I'm using). This shows up on the VU meters in rakarrack and Guitarix.
  • If I set both input and output to RigKontrol3, I get what I described in the first post--a trill that occupies the midrange (sometimes it changes pitch), plus a very-high-frequency ringing. I would expect a bit of hissing or buzzing with the signal hitting all the different gain stages in the software, but this is just weird.
So I'm thinking the problem has something to do with the USB interface or the way it's interacting with the sound chip or some other onboard device.

Shadow_7
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Posts: 169
Joined: Tue Jun 08, 2010 3:35 pm

Re: Noise through JACK on MacBook

Post by Shadow_7 »

It could be that the USB device is drawing more juice than your USB bus can provide. Laptop USB bus's tend to be under powered to conserve battery life. Perhaps a powered USB hub with a higher amp rating could quiet the beast.

http://www.native-instruments.com/en/pr ... -hardware/
http://www.native-instruments.com/en/pr ... fications/

wesrtx
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Joined: Sun Dec 08, 2013 3:45 pm

Re: Noise through JACK on MacBook

Post by wesrtx »

Well, I bought a Plugable 7-port USB hub (3 A) for about $25. I figured if it didn't fix the problem, it's a nice addition anyway.

I plugged everything up, and it works great. But...didn't get rid of the noise!

I also noticed that, depending on where I plug the mouse, I can hear a subtle high-frequency noise when I move it around.

My guess is that it's an issue with the way the USB ports in the computer are grounded/shielded, so electrical noise from other components is bleeding through. I don't know what to do about that besides get a new computer and hope it doesn't have the same problem. This wasn't an issue in OS X, so maybe it's a problem with the USB driver. I will say I get an error every time I boot Linux that says it was unable to load the iSight firmware (technically that device uses the USB interface). Might not hurt to fix that.

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