I have been using the predecessor of the Audio 4c, the iConnectAudio4+ for many years now and absolutely love it. The main issue with that one has been the arrival of the USB C standard, and the fact my iPad Pro needs more power than what the Audio4+ can deliver. The Audio4c can feed the iPad directly from the USB C port. So in order to simplify my cabling, eliminating the need to have a separate power supply for the ipad and use an adapter to connect to both the sound module and the power supply, I decided to upgrade to the audio 4c. Big mistake!
I have been running into several issues with the new unit.
First of all when I turn on the unit with the speakers connected I get a large "bang" in my speakers. Something I never experienced with the Audio4+, contacted Thoman on this and they advised me this was "normal". Secondly I find the unit regularly disappears from Auracle. I only can restore the connection by switching the unit off and back on (Whilst making sure I switch all the connected speakers off first! - I installed a separate switch for my speaker for that sole purpose). Then I frequently lose the midi connection from my digital piano. Again, the only thing that helps is to switch the unit off and on again. So after many frustrations I have now decided to abandon the new unit and live with the extra cables to my Audio4+.
The Audio 4c was an absolute waste of money, and unfortunately I have passed the 30 days return window. So it will be gathering dust somwhere in a corner. Shame!!