Audio routing issues with USB hub and iPhone

eks

Hello,

First off: this is a fantastic app and I’m glad I found it!

I am having an audio routing issue that I don’t see covered in any other posts. If you have any advice or insight on this I would appreciate it.

My setup involves connecting two devices to Stage Traxx via USB:

Behringer X18 Air (sending multitrack song from Song Traxx to mixer inputs)
Ampero Stomp II (sending MIDI program changes from Song Traxx to Ampero)

The Ampero can also act as an audio interface but I am not using it that way. I am sending audio from the Ampero’s analog outputs to the mixer.

This works reliably with my Mac but has some quirks with iPhone.

With the Mac there is a setting to select the audio device in the Mac Settings app. It shows the Xair, Ampero, and Mac speakers as options. If I select Xair, then go to the Audio Routing settings in Stage Traxx, I have the option to select the appropriate Xair channels. The Ampero does not show up at all.

Everything works great this way.

If I instead plug the hub into my iPhone, the behavior is different. Stage Traxx only shows the Ampero channels as options for routing audio. If I unplug the Xair from the hub and then re-plug it in (essentially I have to make sure the Xair is connected after the Ampero), the Ampero channels go away and the Xair channels show up as options. From there, everything works fine for a while. After some time, the Xair channels disappear (and the Ampero channels are shown) until I unplug/replug the Xair.

Thanks again for any help you can offer.

Regards,
Errol

peter

That's an iOS limitation. iOS can only use a single audio interface and the last connected is always the one that is selected.

Fortunately there is an easy workaround for your setup: Just connect the X18 and use that as a midi interface. Connect your Ampero with regular midi cables to the X18.

eks

I thought that might be the case, but I wasn't able to find anything specifically saying that from any of my searches -- thanks for confirming!

I have continued experimenting and it seems to be stable as long as I:

Plug in the X18 to the hub last
Don't let too much time pass without playing audio (I haven't figure out the exact time-out)

Thanks for the workaround suggestion. If I find the above setup to be unreliable I will pick up a USB-DIN MIDI adaptor and try that.

peter

Version 3.7 will have a setting to keep the audio engine active even when in background. That will prevent iOS from disabling any audio interfaces.