Suffice it to say that the 33.8688MHz clock is an internal property of the D/A converter, and these kinds of converters are often marketed as "1-bit" or "MASH".
Basically, they are easier to mass-produce because they don't have to rely on calibrated components to output precise voltages. Instead, they just have one voltage level that is sputtered out very quickly (33.8688 sputters per second) so that the average value is precise.
Nevermind a bullet in the head. Here's an alternative
http://www.stereophile.com/showarchives.cgi?374:4
-JNS