AU UI Problem

Firstly, I m using Mixbus in case that has any relevance to this problem. I could try original Ardour but I don’t see how this could be a Mixbus only problem. I am using a Macbook Pro 2008 model.

When I have AU UIs open and open another Ardour project I am left with white squares where the AUs UIs were. This is permanent across any app on the desktop until I shut down Ardour. It happens with all plugins.

I am also using OSX 10.6.3

@efflux: what version of Mixbus? and which AU’s?

Hi Paul.

It’s Mixbus 1.2 and Ardour 2.8.8.

This is a new system so I don’t currently have lots of plugs installed. I won’t be using lots anyway but I have EOS Reverb and most of the Ohmforce plugins installed. Since these are all showing the problem I am assuming it will be any AU plug with it’s on graphical UI. The Apple AUs are OK even when it appears to have it’s own UI like the delay.

I might find some other AUs to test.

Should I install Ardour non Mixbus? I have a few other issues related to AU plugs. Some may just be Mixbus. I’m not sure if I’m supposed to be discussing this here but I will be hammering Ardour every which way now so if there problems I will find.

Just tested another free AU. Destroy FX Geometer. Same issue.

By the way, this problem is not a killer. You just need to close the AU UI window before opening a new project.

However, there are some other problems I need to discuss.

Just another point. Is there a good and free (or cheap) app I can use simply to test AUs before I know any issue is with Ardour? I have no Garage Band on here. I did a fresh install of OSX 10.6.3. I used to have Logic but don’t have that anymore. If there is a simple host for just AUs, that could be useful to me anyway.

Another point is that I have an SSD drive on here. This Mac’s SATA II is in fact limited in speed to SATA I. Even some of the new ones have been! I did investigate all this though. Issues with clearing up the garbage on the SSD etc. I fitted an OCZ Vertex which actually has a read speed beyond my SATA controller but the rest is fine. Performance is amazing! I have had no problems with this and no noise from a drive.

@efflux: this issue was solved in Mixbus 1.2 (it was a problem with 1.1). I have tested all the DestroyFX plugins here, and they all work fine here. Are you certain that you’re not using an older version of Mixbus by mistake? Its also possible that I have not tested the precise steps that you followed - will do once I can test again.

Oh, and the set of plugins that are affected are those that have Carbon-based GUIs (an older programming interface from Apple) rather than Cocoa GUIs (the current interface that Apple recommends).

Apple provides an app called AULab for developers which is intended as an AU test host, but its really quite a powerful program all by itself (vaguely equivalent to Ardour’s mixer window). I’m not sure if its installed unless you have the developer tools.

@Paul I think you missed something important in the post, he is closing the session while leaving the AU UIs open, and opening a new session without exiting Mixbus.

@efflux Going off memory some issues/glitches were discovered with closing a session and opening a new one without exiting Mixbus entirely. I would suggest that you go ahead and close Mixbus and reopen to switch sessions for the time being. Sorry.


Thanks. I will check out that app or find a way to install.

I need something like this to test with.

For example, with some plugins, when I have stereo plugins in the same channel and I bypass one then the effects before this bypassed one turn to mono. If I activate again or delete the plugin then the full path turns back to stereo. These are all full stereo plugins and clearly function as such when activated.

It’s definitely Mixbus 1.2. I’ve checked.

I haven’t looked into the Carbon Based GUIs but Destroy FX Geometer definitely has the problem.

Replicating it on my system is simple and it always happens. If I have a plugin window open then I open a new Ardour project I am left with a white square where the plugins UI was. This square never disappears from the desktop until I close Mixbus.

Come to think of it now. Something is wrong with this stereo to mono thing because I have tested the vst versions of these same plugins chained in FL Studio on Windows and this does not happen so hence I need to check if this is an AU problem.

Hi seablade.

I didn’t see your post there. This UI thing isn’t a major issue. It’s likely I will not be opening lots of different Ardour projects anyway but I just thought I’d post about t.

Opening a new Mixbus session from scratch is no problem here. Happens in a few seconds. The beauty of SSD :). When I got this computer (second hand) it still had Logic and Protools on it. Opening those from a non SSD drive :(.


I managed to get that AULab and without installing the whole of Xcode.

This is cool just for running AUs. Simple and no unnecessary features.

Plugins are all working correctly as far as bypassing in AULab is concerned. Some do not work right in Ardour. Stereo is changed to Mono.

An example would be Ohmboyz delay then Eos Reverb. When I bypass Eos, Ohmboyz becomes mono. The Apple AU reverb does the same thing. Not all plugins seem to be effected. I will have to test more.

Here is how to replicate it for free.

Install Destroy FX Skidder. Open that anywhere in Ardour (Mixbus) then turn the spread to full. Make sure you can hear the stereo effect. Then open Apple AUMatrixReverb after Skidder in the channel. Depending on where you open it (insert or send) you may need to adjust dry/wet mix to hear stereo from Skidder clearly. Bypass AUMatrixReverb and Skidder becomes mono. This does not happen in AU Lab.

Hi all,

To add an extra information to Paul’s answer concerning AU test software: Apple provides also a command-line utility named “auval”, which is very useful. It’s included in the Developer Tools, and I guess also in Logic.