Gradual MainStage Audio Degredation

samandersonmusic · Post by **samandersonmusic** » Fri Jan 25, 2019 6:59 am

Hello everyone. Here's the rundown.

I spent a season using MainStage (version 3.0 or 3.1, I believe) to host Sample Modeling, Audio Modeling Contact patches with my Kronos 2 (V 3.0.4) acting as an audio interface. The setup was lovely. Stable, streamlined and sounding great. I decided to upgrade my OS from Mountain Lion 10.8.5 to High Sierra because my web browsers could no longer handle basic tasks. I upgraded my OS and MainStage auto upgraded to version 3.4.2. Ever since the upgrade, MainStage and my Kronos no longer play nicely. After about 10 minutes, the audio transferring from MainStage through my Kronos USB begins to distort. Subtle at first, it eventually becomes unrecognizable. I believe that I have it pinned down to a problem with MainStage and I'm almost sure its sample rate related but I'm at a loss of how to fix it. Here are steps I've taken to troubleshoot:

New USB cable (no change)
New USB port (no change)
Tried USB hub (no change)
Checked to see MainStage is running at 48 kHz
Changed I/O buffer to 1024 (no change)
Experimented with MIDI clock settings
Turned audio on/off

I took my computer to an Apple Store. They wiped it and reinstalled the OS. I re downloaded MainStage and tried a fresh patch. The problem persists.

Music from my laptop streams perfectly fine. Once a blank MainStage concert is opened, the laptop audio outside the application also starts to degrade. Once I quit MainStage, it returns to normal.

The problem DOES NOT occur when I use my interface to drive the audio. It's a relief that I have a backup plan, but I don't want to carry an interface long-term when Kronos has that availability so conveniently built in.

Any ideas? The two HAVE to be compatible, right? Maybe a missing driver? I'm totally stumped. My next plan is to update my Kronos from 3.0.4 to 3.1.2 but I'm kind of hesitant to jump down another update rabbit-hole. I suppose if I can't figure it out I can use Time Machine to go back but it would be nice to be able to use the internet AND MainStage.

All ideas and experiences welcome! Y'all are my last hope.

mikelees · Post by **mikelees** » Fri Jan 25, 2019 7:36 am

Hi,
That sounds exactly like the Apple core audio USB bug that many of us here experienced with Kronos. It was fixed in a later version of High Sierra - would have to do some digging to remember exactly which version. Some searching on this forum may find it...

Poseidon · Post by **Poseidon** » Fri Jan 25, 2019 9:33 am

Apple core audio USB bug ?

Not entirely true.
Of course there might be bugs, we will never have a perfect one, but the main cause is more than that.

Beginning with 10.11 Apple has completely rewritten the USB drivers that employ the use of ACPI to a much greater extent. Imperfections in ACPI implementation are the main cause of troubles.
Many Devs took shortcuts to save money and didn't follow Apple's hardware design guidelines.
Those who followed they have actually benefited, e.g. Stardom, RME.

Regarding the fix, I would recommend you to take closer picture at your issue - use CONSOLE and study the log.

SeedyLee · Post by **SeedyLee** » Fri Jan 25, 2019 11:23 am

I had the exact same issue with Sierra and High Sierra, and it affected not just the Kronos but many other “class compliant” audio devices as well.

The problem seems to be resolved in Mojave.

If you don’t want to upgrade, you can copy the USB audio driver from a Mavericks, but it’s a bit more stuffing about.