Quote:
Originally Posted by claymon
... what is it about getting the signal from digital to analog that improves the sound so much? And what do these $200 DAC's do so much better than a cheap one?

DACs are actually more complicated than they sound. The problem is that the digital sampling data you have only specifies points  what the line voltage was at the *instant* the analogtodigital converter took the measurement.
Somehow you have to turn this collection of voltage readings back into the original signal.
Straight interpolation would give you a straight line. This works fine for low frequencies because you've got so many sample points for each wave cycle (ie.. at 100hz, each wave gets sampled 440 times at 44khz sample rate). The straight lines work fine.
When you get to high frequency signals (ie 5khz), your number of data points per wave cycle drops dramatically. Straight lines won't work; they introduce all kinds of nastiness. Instead of a smooth curve, you get something like a jagged rock.
There are mathematical solutions to the problem which provide better (curved) interpolation based on historical and future values, and all sorts of complicated tables. The better the algorithms, the better the DAC.
Then there's the analog path itself. Component choice and quality affects analog bandwidth, accuracy, decay rates for capacitors (which can depend on the amp's internal impedance, etc.)
It's NOT simple to do DACs right!
And that's where the cost comes from.