I have been promising you guys a review of the Weiss DAC 204 and here it is. The real question is the comparison vs. the 501/502. I don't have a 501/502 here at the moment for comparison. I do have the Helios which is a bit unfair.
Packaging is kind of lame. It is in a simple cardboard box with recycled, shredded paper as the protective material. For $3500, I expect foam. Maybe this is greener????
Tonally, this unit is a Weiss. It is not perfectly neutral and drifts a hair forward like other Weiss products. The sound is similar as well. The unit is detailed and sounds quite revealing. The image has good depth and width.
In a Sentimental Mood had sparkly piano and excellent placement of instruments. Be Still My Beating Heart has scale. Sting's voice is not sibilant in my system, but I think in a slightly brighter setup it could drift that way. Liberty sounds clear with very black background. Again, no sibilance. The noise floor is quite low on this. Great detail with Duende and the unit appears to be able to keep up with the more complex portions of the song. The Berg piece sounds right sized and intimate.
Based on my notes, I am not seeing hug differences between the 204 and 501/502. All indications are the 501/502 are a bit more detailed and the image is more stable. That said, I can't say that with absolute certainty.