Constant crackling on USB optical audio output (Edirol UA-1D)
I have a Edirol UA-1D USB digital optical and coax (SPDIF) audio device, hooked up by optical cable to an amp for playing music. No input is connected to the device. When the OS 10.4.5 iMac it is connected to is booted the device works fine, but after a while the output suddenly starts containing constant repetitive crackling on top of the audio. It may take 10 minutes for it to start, it may take an hour, it may even sometimes take several hours but it always starts sooner or later. Sometimes it eventually self-heals (to then start again sooner or later), sometimes not. It seems to happen randomly, there appears to be no association with any trigger event causing the noise to start.
Stopping iTunes audio output does not fix it nor does switching the sound output device back to the internal speaker then back to the Edirol. The only thing which stops it is disconnecting the device from the USB bus then reconnecting it, or rebooting OS X.
The same iMac can also boot MacOS 9.2.2 and Yellow Dog Linux 4.0.1. Without changing the hardware configuration I have had the Mac run MacOS 9.2.2 for a day using iTunes to play out on the same audio device, and I've had it running Yellow Dog Linux for 5 days using Amarok as the iTunes stand-in, and the Edirol has worked perfectly under both these OSs, suggesting that neither the Edirol nor the USB bus or hardware configuration is the cause of the problem.
I have done a complete clean (volume erase) reinstall of OS 10.4 from the distribution DVD thinking that there may be some kind of corruption or 3rd party software conflict on my main 10.4 volume, but the problem still happens in exactly the same way every time when booting from the clean volume.
I downloaded the AppleUSBAudio.kext extension source from www.opensource.apple.com, built it with extra logging enabled and installed it (it now generates lots of console logs when audio is started and stopped) to see if it logs anything when the crackling starts. It doesn't.
Has anyone else had these kind of problems and found any solutions? Does anyone have any hints as to what might be causing this to happen and what a possible solution might be? Please don't say "switch to Linux"...
iMac G4 800MHz Mac OS X (10.4.5)
Stopping iTunes audio output does not fix it nor does switching the sound output device back to the internal speaker then back to the Edirol. The only thing which stops it is disconnecting the device from the USB bus then reconnecting it, or rebooting OS X.
The same iMac can also boot MacOS 9.2.2 and Yellow Dog Linux 4.0.1. Without changing the hardware configuration I have had the Mac run MacOS 9.2.2 for a day using iTunes to play out on the same audio device, and I've had it running Yellow Dog Linux for 5 days using Amarok as the iTunes stand-in, and the Edirol has worked perfectly under both these OSs, suggesting that neither the Edirol nor the USB bus or hardware configuration is the cause of the problem.
I have done a complete clean (volume erase) reinstall of OS 10.4 from the distribution DVD thinking that there may be some kind of corruption or 3rd party software conflict on my main 10.4 volume, but the problem still happens in exactly the same way every time when booting from the clean volume.
I downloaded the AppleUSBAudio.kext extension source from www.opensource.apple.com, built it with extra logging enabled and installed it (it now generates lots of console logs when audio is started and stopped) to see if it logs anything when the crackling starts. It doesn't.
Has anyone else had these kind of problems and found any solutions? Does anyone have any hints as to what might be causing this to happen and what a possible solution might be? Please don't say "switch to Linux"...
iMac G4 800MHz Mac OS X (10.4.5)
