USB-DAC
A very flexible solution is a USB-DAC as almost any PC offers USB.
Using a USB DAC you don't need a sound card at all.
If you use a laptop this is probably the way to go if you want to improve on the onboard sound card.
A clear and well written step by step guide to setup and USB DAC using XP, Vista or OSX can be found at the Ayre website.
Setup for Win7.
Setup for Vista.
Asynchronous USB 2 DACs
USB Audio class 1 is limited to 24 bits/ 96 kHz maximum.
This is what fits into USB Full Speed mode so 12 MHz (USB 1).
To play higher sample rates the High Speed mode (USB 2, 480 MHz) is needed.
From mid-2010 on both OSX and Linux supports USB audio class 2 natively.
If the DAC is USB audio class 2 compliant it will play up to 32/384 on these systems without the need to install additional drivers.
Microsoft doesn't have a native mode USB Audio class 2 driver. You need to install a third party Class 2 Audio driver at the PC side.
All DACs listed in this section requires USB 2 (High Speed).
The fact that they do need USB 2 (High Speed) does not necessarily imply they are also USB audio class 2 compliant.
A couple of models
24 bit Asynchronous USB Class One Audio DACs
These DAC’s are USB Audio class 1 compliant.
They can play 24 bits audio with a 96 kHz sample rate.
All major operating systems (Win, OSX and Linux) do have native mode USB Audio class 1 drivers.
A couple of models.
24 bit adaptive mode USB Class One Audio DACs
These DACs use the adaptive mode and are USB Audio class 1 compliant.
The audiophile community thinks asynchronous is the way to go.
So all of a sudden these DAC’s look obsolete.
However, as usual in technology, the implementation is very important.
A good adaptive mode implementation can beat a mediocre asynchronous implementation.
Some say that the difference between async and adaptive is simply marketing talk.
As faith would have it, prominent spokesman of these view are the ones making a living by selling adaptive mode implementations. Surprise….
A couple of models.
16 bit USB
Today you can buy a 24 bit USB DAC at an affordable price.
No reason to limit you to 16 bit anymore.
16 bit USB DACs can be found here.
More technical information about USB audio can be found here.