Logic Pro 9.1.7 + Imac 2010 + 10.7.4 + Firewire = Audio Error and Solution.

Question

Hi all,
This post is the end of a weeks long hair pulling, to save other people the pain of my past week, here is a quick rundown of the issue and the solution that for us at least worked.
All the software is legit and fully updated btw, before people ask.
Logic Pro 9.1.7 on 2010 Imac on 10.6.x, Refx Nexus, Sylenth plus many other VST's and Au's, Mackie Pro + Extender, 2 Midi Keyboards (Oxygen 49 and Alexis 49)  and with a M-Audio 410 external soundcard running 10.1.3 driver, all working.. only issue we had was when copying midi between tracks into differing plugins the midi would corrupt the plugin requiring a restart of Logic.
This error we later discovered was due to midi automation for plugins being copied over, but that is not this issue.
Updated OS from 10.6 to 10.7.4 by way of 10.7.4 Combi Update. Removed M-Audio Drivers and then installed 10.7.4,
Installed brand new GRAID 4TB external disk (Raid 0 at 64kb block sixe) and connected M-Audio 410 via daisy chain.
Installed M-Audio Drivers, all ok.. at first..
Graid is 800, M-Audio is 400.. Connected as Imac -> GRaid -> Maudio
At first, its good, no issues.
Copied over a whopping 550GB off Imac onto external..  then later on, rebooted mac and started working on music.
Ran Logic Pro  (64bit mode), whilst using Midi with Nexus we discovered the Audio at first was ok, but quickly over time degraded to where the sounds started becoming distorted, the more we went on, the more the distortion increased, after a while the midi notes were just sounding awful.
Rebooted mac
Started using Logic again, not 1 minute in, External drive and M-Audio disconnected themselves from the Mac.
Rebooted
Hard drive now seen, no M-Audio.
Now though, even using Itunes or Quicktime or VLC on any mp3 via internal soundcard, quality was.. well terrible. Within 2 seconds of hitting play, you knew it was bad.
Shutdown, removed external drive from chain, rebooted Mac -> M-Audio
M-Audio now seen, sound quality dreadful, shutdown Mac, rebooted without M-Audio, sound still awful just on Internal audio.
Time passes, I smoke too much, prod and poke and eventually reach for the install media
(Lots of shutdowns and restarts in next bit, after each line, also carefully reset and tested every Audio setting.)
Removed M-Audio driver
Installed 10.7.4
Installed M-Audio
All good again.
Later, as a test, connected External drive on its own, no M-Audio
All good.
Second test, added External Drive plus chain to M-Audio
Not good, M-Audio seen but even though sound bars showing on M-Audio software, no sound out to mixer
Removed External Drive from Chain, M-Audio now straight to Mac.
All BAD; sound was terrible,
Disconnected M-Audio
Playing any Mp3 via internal Audio, terrible..
Whatever happened, has thrown the entire Audio system into a mess, again!.
Removed M-Audio driver.
Reinstalled 10.7.4
Reinstalled M-Audio Driver
All good, on internal or external Audio
Disconnected M-Audio
Reconnected External Drive Only
Drive OK, Internal Sound OK.
Removed External drive
Reconnected M-Audio
All ok, internal or External.
Ok, Final conclusion.
When the M-Audio (400FW) is connected to Mac via External Drive (800) the Audio is knackered from that point onwards on 10.7.4, removing M-Audio drivers and re-installing makes no difference, even the Internal Sound is knackered.
Only solution at this point, remove M-Audio driver, reboot, reinstall 10.7.4, reboot, reinstall M-Audio Driver, reboot.
Then its all good again.
My guess is this, and I am probably wrong but it is all I can think of.
When the M-Audio is daisychained the Mac changes a setting somewhere, probably to adjust for high latency, at this point it is written somewhere (either as a file or as DSP bios setting) that is not being reset.
This is why it is completely broken until 10.7.4 is re-installed at which point whatever setting it is that was changed, is reset.
This is all I can think of, I have posted this so that if someone else in the weeks ahead has a similar issue, it will save you the stress and late nights I had this past week.
Take care all.

Answer 1

I was seeing the same problem... I'm a new Logic user, switching from DP, and so it was a minty fresh install of Logic Pro 9.1.7 under ML.
It turned out to be a third party graphics driver that was screwing up some internal process:  specifically, the dirver for AirDisplay, an iOS app that lets you use an iPad as a portable monitor.  When I removed the driver, the problem cleared up instantly, and I have done 9 hour sessions in Logic since then without a single hiccup.
If you're running a third party driver, remove it, repair permissions and see if the problem clears up.