Thanks, and yes, all of my observations are based on my own music library, IEMs and preferences. I probably should have included my music test tracks, but in the end I decided to keep my IEMs out of the review and give a more high level view of what I think the R52 has to offer in general.Nice review. Glad I'm not a real audiophile as eco-mode sounds fine to me with the benefit of 30hr battery life. Yes, the A amp sounds better even with my easy drive IEM's but not a must use feature for me. I do tend to like Sabre DAC's.
The 'criticisms' I noted were written after many, many hours of A/B comparisons with other DAPs. On its own and before comparing, I found the R52, even in eco mode, a very pleasant listen. Paired with my cheapie BLONs, I can happily listen all day without any complaints. I guess it's the same way you heard it...but no contest once you heard the WM1ZM2 side by side (at almost 10x the price!).
I really like how HiBy is testing out new tech with the midrange DAPs, so hopefully the Class A stuff will filter up to future flagships. An R2R DAP with Class A will be yummy indeed!