UPDATE:. Now supports up to 24 bit and works pretty well. Changing to 4 Stars.
Does not support Amazon Music Ultra High Definition audio, which I confirmed with Amazon customer service. I only bought this for that one reason, as my 4K fire stick is just fine. The spec sheet states it supports ultra (well FLAC), and it did for a few days after I received it. Amazon did an update and now will only support HD, not Ultra. Makes no sense and I think they are deceitful with how they are advertising both the cube and music.
Very sad you cannot use an Amazon product to get the most out of an Amazon product! Chew on that for a minute.