I built the Blueshift and the Flintlock. I also posted threads on both circuits, as they were complex builds. They're both amazing, among the best effects i ever tried, In my experience, they are the best modulation effects I could find on musikding in terms of sound quality.
I didn't order the Countdown, looks great but I built three phasers already... none has 10 stages, though.
The Flintlock takes a bit more time to be correctly calibrated. Instructions are clear, but I had to spend some time on the circuit, to get familiar with most trimmers, understanding how they acts on the circuit. I lowered the sweep on high frequencies (from 2.6Mhz to 2.2Mhz) to avoid distortions in the top end of the sweep.
I was very motivated to get the best sounds I could from the Flintllock, because, even uncalibrated, it sounds very beautiful and promising.
The Blueshift : I thought it would be the best chorus ever : it's meeting all my expectations and more...
I noticed Flintlock and Blueshift can put to rest an everlasting quest, for a while. The hunger for the "best flanger" and "best chorus", is generously fed.
About this Echo DC build : Everything is soldered, sanitized, cauterized, I am just waiting for one last chip, and i'll start the biasing process.