DAC = thin sound

First, rip CD's using XLD to AIFF. Never use ALAC format. Second, install a decent playback software such as Audirvana, Pure Music or Amarra.

Finally, you may never get great sound using those interfaces. I've not heard them myself. You may need an upgrade USB converter or reclocker. The master clock in these interfaces is the most important part of any digital playback system, more important than the DAC itself.

More tips here (no advertising):
http://www.empiricalaudio.com/computer-audio/

Steve N.
Empirical Audio

thanks Steve :)

I thought ALAC is not compressed file? All my CD's where ripped thru ALAC..

About the interface I'm using-- yeah kinda have feeling about it. BUT right now I'm in fund "saving" mode. I plan to replace my macbook hopefully after August and I would get the cheaper USB to S/PDIF converter either the hiface2 or the halide design bridge..

ALAC is compressed, but lossless. It still impacts sound quality when using USB or S/PDIF from a Mac. AIFF is better, but also not without fault. I wish Apple would fix this. Only .wav is unscathed by the software.

Steve N.
Empirical Audio

IMHO, the USB implementation on the DL III is not great. I had to buy a Vlink to get close to my Denon transport in sound quality when using my laptop as a transport. With the proper PC software I was able to best the Denon-DL III sound quality. All that said, my system still sounds really bright to my ears. Haven't solved it yet.
I am not able to hear a sound improvement between audio formats, I think this is dependant upon the system, but it is a cheap tweak to try. I also cannot hear a difference between glass toslink and digital coax, maybe it is my hearing!

I have an AppleTV connected to a V-dac with toslink. The tone density increased when I used a shorter glass toslink cable that I bought on amazon, and when I changed interconnects from the V-dac.

I run Apple lossless files, but I even get good heft and tone from some MP3's that are well recorded.

I would start out playing with cables, toslink first.

Speaker positioning may be an issue also. I recall I had to change the toe-in to return to a coherent sound after the switch from a CD Player. Don't ask me why.