Ardour to Mixbus and back again

Having bought Mixbus on special offer at Christmas I thought I’d see if there was any audible difference.
Opened a session in Ardour, exported the track, then opened the same session in Mixbus, exported, then phase inverted one against the other in a new session. They should have cancelled out, BUT what I was left with was the sound one of the reverb buses. I tried a few more times muting various tracks, but my audio buss 2 was always there as a ghosty remnant. I wondered if somehow one or the other DAW had inverted the phase of the buss.

Anyway… I’d love to report further but at some point I hit SAVE in Mixbus. This is where I need help! Now when I open the session in Ardour, (in addition to all of the stub plugins and extra busses), the Master can’t see any hardware output. The connection manager doesn’t list Master out as a bus - I can’t ‘Add audio port’ at the bottom of the fader (nothing happens - only the MIDI outputs are listed). I can create a new audio buss and route that to my interface so the hardware is working…

Helpful suggestions gratefully received. Thanks.

Sorry I don’t have any ideas to fix the problem you encountered, but in terms of running a null test to see if there are any audible differences between Mixbus and Ardour (or any other DAW), this test has been run many times (I remember seeing some posts on the Mixbus forum) and as expected there are no differences between Mixbus and any other DAW until you engage the channel strip emulation in the mixer (e.g., by activating the EQ).

That’s what I was expecting, but I hadn’t got as far as switching on the channel strip elements (eq, compression). I was making sure I got null first.

You can load an Ardour session in Mixbus, but the other way around is tricky. You’ll loose all routing information which is internal in Mixbus.

Also as you have noticed Mixbus/Master are special. It should be possible to manually edit the session file (XML in a text editor) to remove all the elements and re-add a master-bus with direct inputs.

Have you checked the backup folder? or simply the *.ardour.bak file (previously saved session)? In case you’ve only saved once. That should still be the original ardour session.

Thanks Robin. I’ll have a look later and see if I can retrieve it

I tried again.
Open new Ardour session, add 1 mono Audio track, 1 stereo Audio bus.
Put a short click sound on the audio track, send to reverb plugin on the audio bus
Export audio from Ardour
Open up the same session in Mixbus and straight away export audio
Put both resulting files on 2 tracks in a clean session, phase invert one track
…with some reverbs, there’s some reverb remaining, with others (or no plugin), everything is cancelled as expected.
Of course ACE reverb is one of the well behaved ones!
If I have time I’ll investigate further - I wonder if Mixbus is picking up a different (VST, VST3, AU) version of the plugin… Or do some plugins work with some sort of randomisation that is different every time?

Yes, some reverbs do. Also some free running effects like phasor of flanger, could be different. Some plugins rest their internal LFO when the transport stops (or starts).

That all makes sense then. The convolution reverbs cancelled out nicely and those with modulation didn’t.