The reason is that he did an experiment (with a DAC he built), and he prefers the sound using the Windows mixer, with minimal amount of other software running.

ASIO is a popular method for achieving supposedly bit-perfect transfer, but the reality is we never know how good ASIO does the processing of the data itself. Let me explain some just had a discussion with a friend regarding bit perfect playback on windows, and I think there isn't a clear answer. It satisfies all the basic requirements of a good DAC, and for $179, I hardly think that you can do any better. But you know what, I truly think that the HUD-MX1 is a great DAC for the price. (I’ll defintely write a comparison between the two, once the uDAC is here). I’m still waiting to get a Nuforce uDAC, which is repotedly to be very good for $99, but the uDAC hasn’t arrived, and so I have to write this review apart from the uDAC. So far, my experiences with DACs has been limited to mostly higher end units, and frankly speaking, it’s hard to get excited about a $179 stand alone DAC. The HUD-MX1 is the lowest priced stand alone DAC that has come to our test room. Its dimensions are quite compact, as you can see at the photo below, positioned next to the Ipod. While DACs with a more “audiophile” sound signature with thick bottom end and warm sound are nice, sometimes you want a more neutral DAC for pairing with a tube amp, to avoid having a sound that’s too thick or too warm. Now that may sound like a “generic” description that I could’ve copied and pasted from some other reviews, but the fact is the HUD-MX1 is a plain, uncolored DAC that simply does its job very well. There isn’t a strong bias toward a certain frequency region, neither are any frequency bumps or spikes present. Detail level is very good, although nothing to get goosebumps about. It’s free from any obvious coloration and digital artifacts. Sound wise, the HUD-MX1 is very good, considering the price level that it’s being sold for.

Audioengine d1 dac hd598