NDS vs NDX+ DAC/555PS

I know this has been covered before when the NDS came out (S in S made a detailed comparison).  Perfectly happy about the NDX set up except that three boxes bothered me.  The opportunity to acquire a NDS came along and I purchased it without auditioning.

After letting it warm up I played a few classical tracks and wasn't blown away.  

I played:  Liszt Sonata in Bb (Argerich), Beethoven 12th String Quartet and Walton 1st String Quartet, which is new to me.

It was as if I was sitting at the back of the room rather than right in front of the musicians compared to the NDX.  I put the NDX set up back on and received the familiar performance.

Oh dear, bad news re NDS.

I did the same again today. Starting with NDS.  It sounded great.  As if the auditorium was truly quiet. I then put on the NDX again and once again, the familiar up front performance. But what contributes to that nature is some sort of noise which isn't  in the music but which is added by the NDX system. What I thought was bringing me closer to the musicians doesn't gain me any greater insight into the music or even the feeling that I could better hear and feel the texture of bow on string.  The Walton was key.  Even though the NDS appeared more distant, the music made more sense, the built up tension was better felt. With the NDX playing, yes it was louder , with added body.  But it's as if part of that body is not on the original CD.

I hope that makes sense. I'm happy with the NDS.

I wonder what a 552 would do over a 52?