I have listened again to the two versions of the Reference Amps I have for testing purposes. One has about 150 hours of burn in and the second has about 90 hours of burn in.
The huge cap does make for an interesting evolution of the amps. The overall character changes quite drastically and it is in cycles. I mean one day the highs are predominat and 24 to 48 hours later the highs are subdue, same with the bass. However the amplitude of the cycle peaks and valeys is reduced as the burn in progreses.
In my limited experience with large caps in portable amps it seems that large caps as used in the Reference behave in such a cyclic nature and take a long time to settle. My experience is that a minimun of 400 hours has been needed, although a particular amp took about 800 hours to finally stop changing.
In my opinion this is good in that it allows the user to appreciate and experience the evolution of the amp as well as an appreciation for the design. For someone like me that at times want inmediate satisfaction this amp (and others with large caps) helps in making me appreciate the "ride" and make me more patient. :-)
The sound of the amp as it matures (burns in) is continually shaping the output to one which is more mellow yet it retains a sense of detail and clarity that is closer to a home amp than a portable amp. The bass has a great impact w/o being bloated nor the only thing you hear. To me this last statement is a credit to the design, how many times we listen to am amp that has great bass but that is the only thing that you hear because it overpowers the rest of the frequencies? that is not the case with the Reference Amp. You hear tight and impactful bass while at the same time the clarity and detail of the mids and highs are in the correct proportion as the original recording.
I have great hope that this amp will become a superb addition to most (if not all) individuals who get one and who can appreciate the evolution of the amp over its prolonged burn in period. The rewards are more than worth it. I should mention that all the wonderful and superb sound comes in at a fantastic price with a prolonged battery life, a combination that in my opinion other amps can not achieve. Yes some amps have the same fantastic sound (Supermicro IV), others the fantastic batery life (Tomahawk), and yet others an increadible small size (Supermicro IV) but only the Reference Amp combines all of these qualities in one amp.
As a final coment I would like to address the volume pot. I do not where Dr. Xin found it but I love it. I mean I can have plenty of control with it while listening to IEMs (Shure E500 or V-Moda) or my higher impedence cans (Beyer DT990 in 250 ohms). Other amps resort to a gain switch that although they work they add complexity, cost, and yes noise.
Anyways I hope the above provides a sense of what this amp can do and I hope to provide more input as it matures (reaches the 400 hour mark). Thanks for your time in reading such a long post.