I want people to remember that this is not a "cheap DAC", this is the best I know how to make right now. There is no skimping on anything to a price point. Fortunately I know how to get exceptionally good sound without having to spend thousands of dollars on a single part!
For example this DAC has 6 ultra low noise regulators, they are not cheap (about $7 a piece), but far less than other "top of the line" DACs that use $75 regulators that don't perform any better. Or less expensive DACs that will use 2 $1.20 ones. It gives performance way better than the cheaper ones without the exorbitant prices of the other "statement" DACs.
Oh and Doc, I have a new filter that is significantly better than what you have now. I threw the one in your DAC together in an hour to have something you could hear. A couple weeks ago I spent some time with a friend and we tweaked the filter parameters to significantly improve the sound. By the time we were done it was the best he had ever heard. (and he has a special custom DAC that WAS state of the art)
John S.