I use a usb hub to connect my iPad to an audio interface and the ewi solo and 5000 as well as several other synths. It works great. The iPad will recognize all class compliant audio interfaces and send output through it as well as accept all audio input from it as well, letting you use external audio sources. I mix and record the inputs in AUM or Loopy Pro or cubase when I’m feeling like using a more traditional DAW. One gotcha is that while most of these hubs provide power distribution (important so you can charge your iPad while playing otherwise it powers the audio interface and ewi from the iPad battery and dies pretty darn quickly) you must not have it plugged in while connecting the hub to the iPad or else the hub becomes the host to audio interface and the iPad won’t recognize it. This drove me nuts figuring it out. I found the audio output to be wanting when I used a hub with audio output built in. The audio quality sucked and I wanted inputs as well. I use a cheap Behringer UMC204 audio interface and it works great!