Cause of different sound between dacs

That's too simple.

"08-31-13: Mapman
That's too simple."

I know, but it works.

Grannyring(Bill),
Yes! The power supply and the quality and implementation of the analog output section are huge factors in determining the sound you'll hear. Bill I seconded the high quality active line stage suggestion and I know you've tried direct DAC options, welcome back.
Charles,

I am not able to audition the two. Perhaps someone with experience can comment?

I was very surprised at how much better my K03 sounds, compared to my Berkeley Alpha Dac (1st one). It has much more detail, more resolution, deeper/wider soundstage - I can go on and on - it was just 'better' in every plane. I am thinking power supplys, dacs and analogue output stage are all superior.