If I understood your posting correctly, you obtain good quality sound when the **powered** USB hub is in the chain: is that correct?The sound quality is independent (and good) from whether I have the powered USB hub in the chain or not. But it lasts only for 80 seconds before it switches itself down, respectively is switched down by my IOS 13.3. BTW: I tried to downgrade to IOS 12, but Apple does no longer allow that.
...it may be the case that iOS is somehow re-setting. If that’s what’s happening, it’s a possibly a new security feature: iOS 13.x has a built-in setting used to defeat snooping hardware...Something like this may be happening after 80 seconds, but I have no clue.
As a matter of last resort I have ordered the original (expensive) Apple camera adaptor, i.e. a lightning to USB plus lightning adaptor. Will get it on Saturday and will report.
After I have experienced within these repeated 80 seconds how audibly (and I'm sure not an audiophile guy!) the sound quality to my Sennheiser IE800 ist improved by a good DAC like the Dragonfly, I'm really somewhat desperate to enjoy this for more than 80 seconds...
Am I right to assume, that a reasonably priced Bluetooth adapter does not match the sound quality of a physically connected DAC? Otherwise I might try to circumvent the experienced problems by using a BT connector. If so, are there any recommendations?