UPDATE: I contacted Apple tech support but I am still experiencing the problem, they have escalated it. We tried the following:
- reinstalled GarageBand and OS X
- tried running under a different user account
- disconnected all peripherals
- disconnected ethernet
- Airport is off
- iTunes music plays fine
- there seems to be no way to revert to the OS X and GB versions that came on the machine as there is no longer an installation disc included and the reinstallation process downloads the latest versions
I'm not keen to move to Mavericks and GarageBand 10 yet as it is likely that I'll experience issues with my audio interface or AU instruments (loads of horror stories online).
I have exactly the same problem. My iMac was delivered on 30 october, and after installing everything I started using Logic Pro X, and immediately got dropouts, pops and cracks about once a second or so. (iMac: core i7 3.5, 1TB fusion drive, 8GB). Same problem with Garageband 6.05 and Logic Pro. The iMac came with 10.8.5 installed, and I did not upgrade yet. I am not using any external audio devices, just the iMac built-in speakers.
I have an external disk with a clone of my MacBook Pro (10.8.5) and a second clone upgraded to 10.9 (I like to try things before I upgrade). I started the iMac from the 10.8.5 clone, and no problems. Then I made a second user account on the iMac (on its own drive), tried Garageband, and no problem.
So I inspected my own account and found a Camel Audio plugin that Logic Pro X had already complained about, and removed it. Problem solved, I thought. Everything was sounding fine.
This morning I started up iMac and immediately the problem was there again. Now I could also reproduce it on the second user account and on the 10.8.5 clone. A bit less severe, but if you play a note for a few seconds, there will be a pop. Sometimes it get slightly better after a while. But the problem persists even if I unplug all USB devices
So I tried my next experiment, the 10.9.0 MacBook Pro clone. Amazingly, the problems are now completely gone. It is too early to declare victory, I already thought it was solved yesterday. I am going to test it for a number of hours, and then upgrade the iMac to Mavericks. If the problem comes back, the computer goes back to Apple and I want my money back.
I will keep you informed.
Thank you very much for this information, I really appreciate it!
I like your approach of testing on an external drive first and would like to adopt this practice. I am familiar with making a clone to an external drive (I use SuperDuper) but I am not sure how to boot and run the Mac from this. Is it simply a matter of a key combination during startup?
I am running GuitarRig and various other plugins so would like to make sure they run with Mavericks before commiting to it.
Thanks again for your input.
I use Carbon Copy Cloner, but if you clone is bootable it should show up under System Preferences / Startup disk, if the disk is plugged in. Just select it and restart. There is also a key combination you can use when booting, but
I forgot which one.
Not all clones are bootable, though.
I just restarted my mac from the 10.9.0 clone, and still no problem...
Thanks for the update, I'm glad it's looking better for you.
On my side the plot thickens. I made a bootable clone and when I run using this external hard disk (still on 10.8.5) the noises are virtually gone! Occasionally there is a slight crackle but the application is usable. Of course the performance is extremely slow going over USB to a 5400 RPM drive.
My internal drive is a 1TB Fusion drive so it certainly should be giving GarageBand the data quickly enough, assuming GB doesn't load everything into RAM anyway. I have tried booting from the internal drive and loading the GarageBand project from the external disk but the problem still occurs.
I will now try 10.9 on my internal disk, if I hit major issues I will be able to copy the clone back.
Just an update: the problem did not disappear completely with Mavericks, but after a week of trying it out I decided I can live with it. I hear an occasional pop, about once every few minutes or so. If I were to use my iMac for live performances this would be totally unacceptable, but during editing its is not disastrous.
I tried my two external clone partitions (a slow Samsung disk) again. With 10.8.5 there were a few pops, with 10.9 I could not detect any. This means that this external disk functions better than my internal fusion drive. With the 10.8.5 configuration delivered to me by Apple, with a fresh logic install I heard this: www.nikhef.nl/~t58/AudioBug.m4a
Is the fusion drive to blame? Hard to believe, but what else explains the difference between 10.8.5 on an external and the internal disk?
I started my machine from the external drive running 10.8.5 and didn't hear the noises, then also thought that the Fusion drive was the problem. I afterwards ran a browser, went to YouTube and the problem reappeared, making me think that Flash was somehow impacting the audio. I updated the Flash plugin and this improved things a lot when using the internal speakers however when using the audio interface there are still a lot of noises and recording is not possible.
Finally, the problem is solved. I noticed a line
- Fixes an issue that may cause audio distortion on certain Macs
in the Mavericks 10.9.2 release notes. I am still not sure if this refers to the problem discussed in this thread, but the fact is that it is gone. I have used Logic Pro under 10.9.2 extensively this weekend, for the first time without any cracks and pops.
Under 10.9.1 the problem was still annoying enough that I was considering bringing my brand new iMac to an Apple Store. Fortunately, that won't be necessary anymore. If anyone reads this who helped fixing it, thanks a lot!