I've posted the link before about my 009/HEK/DAVE saga, but for those new to this thread, the key post is here. I've also had plenty to say about tube rolling on the BHSE thread. Yes tubes matter IMO, with or without DAVE. I still have a couple of quads available, so PM me if interested. But to get back to DAVE, I think that DAVE's high transparency and neutrality can be a double-edged sword: It will show up all the good things in your system, but will also show up the bad - there is no hiding place for directly driven headphones if they have FR anomalies (most of them have). And I find that DAVE responds well (or badly) to upstream changes, so I'm not surprised that some find DAVE to be too bright or whatever. My basic components haven't changed for over a year, but I have tweaked the source (see my profile) with s/w, cables, ferrites, grounding. power supplies etc and I've often been surprised by what does and doesn't make a difference. I've made the same headphones sound bright/dull/flat/dynamic/analytical/forgiving/etc with no changes to DAVE or my headphones. I don't know whether this is becuase of DAVE's high transparency (as the Chord team would like us to believe) or because DAVE is not as immune to noise (in its widest sense) as the Chord team would like us to believe. My guess is that's is a combination of both.