Dan Banquer : <font color='#000000'>It's been a few years since I designed and built and outboard DAC but I will attempt to explain. I observed that timing jitter will effect low level linearity in a multibit DAC. Before I start talking directly about this I will fill you in some basics that you may be lacking. For 16 bit audio every bit represents 6 db of dynamic range, so for a 16 bit system we have a 96 db dynamic range. (6 x 16 = 96). When you have a signal that is -60 db below full scale you are now just using the bottom six bits. This is where both Burr-Brown and Analog Devices concluded that dynamic range should be measured. The THD + N at this level should be -36 db ( 8X oversampling will give you an extra 1.5 db to -37.5db, but I don't think anyone has actually achieved that). The dynamic range measurement just adds 60 db to what ever you get for the THD + N at - 60 db below full scale.
So we now know that a near ideal Multi Bit DAC should have a dynamic range of 96 db and the THD + N at -60 db should be -36 db THD + N.
I observed the following. When I was using a Yamaha DIR (Digital interface receiver) my THD + N at -60 db was approximately -32 db THD + N. When that was replaced with a Crystal DIR the measuremant was repeated and the THD +N went to - 36 db THD + N. This is pretty close to ideal.
The major reason for this was the Crystal DIR had less jitter than the Yamaha DIR.
Most DAC's have some kind of jitter attenuation, the real question is how much. One bit DAC's are much more sensitive to timing jitter than multi bit DAC's so it's really all about applications here.
Now in order to be able to appreciate an extra 4 db of dynamic range and less overall lower level distortion you will need a quiet system, a quiet, and well acoustically treated room and speakers that have some decent low level linearity.
The above can be pretty rare in consumer audio.
I hope the explanation helps. It's the best I can do at the moment.
d.b.</font>