Might want to edit the Title, it is an AOS Piccolo.
I have one with a Portable PIMETA and it is an amazing device for the money. I have had mine for about a month now and I am planning to write a review here when I get a moment. I am using my computer as source and it has transformed a pretty decent Apple soundcard into something comparable to a standalone unit (at least my 10 year old Nakamichi CD Player).
Quickly, these are my impressions:
1. Bass is much fuller with great detail, I am using Ety 4S's and there is none of the "I wish these had more bass" feeling that many Ety users exprience.
2. The sound is smoother and sense of space is improved. I am using the LM opamp with it which keeps things more neutral. If you want more sparkle and detail you can put in an AD8620 opamp.
3. The sound is a bit darker and mellow, but with increased detail. With my Ety headphones, this is a great match. If I were using a more laid back headphone I would probably throw the AD8620 in.
4. It creates a nice portable source for your amp. My JMT portable PIMETA sounds fantastic with this. I recently got an Emmeline SR-71 which of course sounds fabulous as well.
4. The AOS Piccolo creates a superior source upgrade to any portable device that I have heard (albeit I haven't thoroughly listened to a lot of portable devices). This makes sense because it is more expensive than most portable devices ($270).
So for the price and portability, I don't think there is a better DAC out there at this price level. If there was something comparable that was truly portable, I never found it and I did a lot or research.
Keep in mind that I was also looking for something I could throw into my computer bag every morning so I could take it with me wherever I go. Hope this helps.
Cheers,
dshea