I just wanted to share my recent experiences with my dac1. My Dac1 was turbo-modded by Steve a year and a half or two ago with full blown mods (which at the time included everything except the now available 627 op-amps and I2S interface). I have really enjoyed this dac since he modded it and when I heard about the new upgrade mod & turboclock 4, I didn't hesitate to send it in. I got it back a week ago and the results are really phenomenal. The first night the sound was a bit congested, but after letting it run overnight I came back the next evening and boy, what a sound. The signature is quite different from before. Vocals are less forward, but there is much, much more detail without a hint of brighness or sibilance. And the soundstage is more 3d with more front to back information. There is also a much more 'musical' character to its sound. I really have trouble ending my listening sessions at night. It is addictive, to say the least. This thing has been keeping me up way too late since it arrived back on my doorstep. Thanks and kudos to Steve, great job!