@join Thank you very much for your input! The powerbank was the right tip!
So with the 3-in-1 adapter, a powerbank and a Y-cable it now works.
I had to plug-in the headphones to the adapter and connect the adapter to the iPhone. Then connect the additional power supply part of the Y-cable with the powerbank, the Y-cable with Sylphyo. Then plug in the Y-cable with power and sylphyo to the adapter.
After doing so I could start Audiobus app and play a software synth (Respiro) with my Sylphyo and a play along over my headphones :-)
All in all it’s not the sleekest solution, but hey - it works.

Thanks again for your support,
Christian

Re: aux-in @Sylphyo for practicing with play-along?
@join unfortunately the solution with the cable splitter for the lightning port seems not to work on my iPhone XS. The sound volume varies and sometimes the sound gets even interrupted. I tried two different cables but both showed the same behavior. But I still like the idea of having a really small ‚mobile rig‘ for practicing with a play-along.
So I thought I could use not the internal sounds but a software synth on the iPhone (Respiro player). I bought an adapter (promate MediaBridge-i) with USB and headphone jack to lightning. But unfortunately the adapter had problems with the USB power. As soon as I connect the Sylphyo the headphone out (USB) vanishes in Audiobus. MIDI seems to work though. I could play Respiro over the iPhone speakers without problem. Adding a power supply at the additional lightning charging port didn‘t help either.
BTW on an iPad USB MIDI and headphone out worked fine in parallel…
Now I have two more ideas left which lead to two questions:
Is it possible to reduce the power consumption of the Sylphyo (charging current) some way, so the it might work with the adapter?
Or
Is it possible to drive a USB to BT MIDI module (e.g. Yamaha or CME) from Sylphyo’s USB port to use the iPhones BT MIDI capabilities? I think for practicing on the go this should be sufficient and also should work without additional power supply.

Or are there any other ideas?

Thank you,
Christian

@peter-ostry Thanks for the info!

I just got my Sylphyo with Sylphyo Link :-)
When I tried the link with headphones the volume was very low. I used Apple EarPods with a 3.5>6.35mm Adapter. The same headphones directly on the Sylphyo were really loud.
Is that a normal behavior?
Is there a possibility to adjust the headphone output volume on the link?
If not, can anyone recommend headphones that work well with the link?
Thanks
Christian

@support_aodyo yes, the pearl edition really looks cool...It has that kind of a 'classic instrument' touch.
But I wonder if there might be any drawbacks compared to the standard model? According to the manual the keybend feature seems to be not yet introduced for the pearl edition. And as there seem to be cutouts in the housing for the pearl pads what about dust and liquids entering the housing?

I haven’t got a Sylphyo yet but I’m currently looking for a new wind controller (I use a WX7 at the moment).
The Sylphyo looks very interesting: lot’s of modulation possibilities, small, lightweight and wireless. In combination with the Link it seems to be great for performance.
For practicing I have a question. With my saxophone I like to practice with play-alongs delivered by an iPhone over wireless BT-headphones. Now I wonder whether that is possible also with a Sylphyo.
As far as I have seen there is no aux-in directly at the Sylphyo like it is at other wind controllers. I assume that the line in of the link box can be used for that purpose. But that would tie me to the Link box and a wall outlet.
Is there any solution that allows to add external audio to the direct headphone output of the Sylphyo? Something like a portable battery powered headphone mixer with a Bluetooth input?
Thanks,
Christian

P.S.: Sorry for the wrong category - it was the only one I could select…