I started with a Scott Nixon Tube DAC with a few Black Gates, but mostly stock. I wasn't real impressed with the sound, so I had a friend of mine modify it... larger chassis; toroidal transformer on-board power supply; cap upgrades all around (including several Black Gates and Nichicon, most of larger than original value), and large-value foil & film coupling caps. Also, a good 75-Ohm input connector. Tube is an Amperex 7308. Much better with the mods, as good as anything I've heard. It leads me to consider that there are many good DACs around, but that most might benefit a lot with some very component upgrades. (Note, however, that the Nixon Tube DAC contains no surface mount devices, so upgrades are relatively simple.)