I’ve been experiencing an annoying problem recently on my MacBook Pro running Mac OS 10.4.11. Any audio played in my DJ application, DJ-1800 v3.0.2, with Pitch Lock turned on, had constant crackles and pops, and was pretty much unusable. Even with Pitch Lock turned off, the crackles were still there if several tracks were played at the same time. It turns out that a recent AirPort Extreme Update was the cause. Fortunately, there is a fix. This article contains full details of the problem, and the fix.
After much investigation, it turned out that this problem is caused by a clash between QuickTime and the recent Airport Extreme 2008-001 Update for Tiger from Apple. This has been reported by several users on the Apple Discussions site, as well as by users on the Ableton forums. The same problem affects other QuickTime-based applications too, such as GarageBand. It’s not obviously affecting iTunes, but unlike DJ-1800 or GarageBand, iTunes isn’t doing anything particularly clever when playing back audio.
The problem only seems to occur on Mac OS 10.4, and not on Mac OS 10.5. It doesn’t look as though the Airport Extreme 2008-001 Update was released for Leopard.
To find out if you have the troublesome Airport Extreme Firmware installed, select “About This Mac” from the Apple menu, and click on “More Info…” in the “About This Mac” window. This will open the System Profiler application. In System Profiler’s left-hand pane, click on “AirPort Card” under the “Network” heading. If it lists a “Wireless Card Firmware Version” higher than “1.1.9.3″, then you will probably be experiencing this problem. (For our machine, the firmware version displayed by System Profiler was “1.3.5″ with the Airport Extreme 2008-001 Update installed.)
The simple (if temporary) fix to the problem is to turn off AirPort when using real-time audio software such as DJ-1800. You can do this from the Airport menu, by selecting “Turn AirPort Off”. This gets rid of the crackles whilst AirPort is turned off.
The more complex fix is to revert back to an earlier version of the Airport Extreme firmware. The previous version was “AirPort Extreme Update 2007-004″. Reverting back to this version isn’t a trivial process, but it’s not too bad. Here’s how I did it.
1) Download the previous Airport Extreme Firmware package from Apple (it’s called “AirPort Extreme Update 2007-004″). Don’t do anything with the downloaded file (AirPortExtremeUpdate2007004.dmg) just yet.
2) Download Pacifist 2.5.2 from the CharlesSoft web site. (Pacifist is a shareware application to restore files from older versions of software. It costs $20, but you don’t have to register in order to do the restore described below.) Many thanks to Charles Srstka for making Pacifist available.
3) Launch Pacifist.app. You’ll have to wait 15 seconds for the trial timeout, then click on “Not Yet”.
4) Click on the “Open Package…” button, and select the AirPort Extreme update file (AirPortExtremeUpdate2007004.dmg).
5) This will open the dmg in a window within Pacifist. Click on the twisty triangle to open “Contents of AirPortExtremeUpdate2007004.pkg”, and keep expanding the triangles until you have expanded to “System > Library > Extensions > IO80211Family.kext”.
6) Highlight “IO80211Family.kext”, and click on the “Install” icon at the top of the Pacifist window. You will be asked if you want to install IO80211Family.kext – click on the Install button to say “yes”. (You should leave the “Use Administrator Privileges” box checked.)
7) You will be asked to enter an administrator’s password. Do so and click “OK”.
8) You will be prompted that “A file already exists at the following location” – click “Replace” to overwrite the existing file. This will happen several times – click “Replace” each time.
9) You can now quit Pacifist.
10) You must now open and run the AirPortExtremeUpdate2007004.pkg installer, and work through the installer as if you were installing the 2007-004 update for the first time. You need to do this step, even though you have effectively just installed the files using Pacifist.
11) Restart your Mac.
After restarting, you should find that System Profiler reports a “Wireless Card Firmware Version” of “1.1.9.3″. The crackles should now be gone! You should obviously notreinstall the Airport Extreme 2008-001 Update if you are subsequently prompted to do so by Software Update.
Update 19th August 2008:
On July 24th 2008, Apple released an AirPort Extreme update to fix this problem. The update is called “AirPort Extreme Update 2008-002″, and is only for users of Intel Macs running Tiger.
Apple’s release notes for this update say: “This update is recommended for all Intel-based Macintosh computers running Mac OS 10.4.11 (Tiger) and improves the reliability of AirPort connections, and compatibility with Logic, MainStage, GarageBand and other audio applications.”
You can install this update via Software Update, or alternatively you can download the update from Apple and install it manually.
Once you have installed this update, you should no longer experience audio dropouts when using Tiger on an Intel Mac with AirPort turned on.