I have about 380 hours on the Holo Spring 3 and it is starting to show its stuff. The articulation is fantastic. Every 24 hours it seems to improve a little more. i will wait till I get over 500 hours as suggested by Tim at Kitsune. to give a final assessment on sound quantity. All in all I am very impressed by this DAC, I hope to acquire the DS Mk2 and compare the two and keep the winner.
Regarding the DDC I have the SingXer SU-1 KTE edition with a very good HDMI cable. I used this for the first 100 hours of burn in. When I switched over to direct USB (PLL On ) it sounded better to me. I will retest this after the 500 hour mark to make a final decision. Regarding the delay in locking up after a bit rate change the USB does not have an issue. It turns out the other inputs can have a few hundred millisecond delay to relock. So if using USB this is a non issue.
Well I am at about at 800 hours and I have to say this unit is incredible, best DAC I have heard.
Up to 500 hours is was good but not really very exciting, just after 500 hours it was like a new set of musicians appeared to show how a piece is really played. Every 100 hours there seems to be another jump in realism. It was like the various instruments came unglued from a 2D plane and evolved into 3D. In many songs it was obvious that the drums and cymbals were very isolated from the instruments. The sound stage got wider and deeper. The giggles keep happening for the last 300 hours. I am not sure if it has fully matured yet, I remember Brett saying that his May was still showing improvements at 1000 hours.