OK, so not Crimson related but am referring to Marv's tube post, I picked up some of those Telefunkens for the Valhalla 2 before reading this, and they do indeed have so many sweet qualities. I didn't do a direct comparison, but my memory wants to say these are a touch less warm sounding than the stock tubes on the V2. Seemingly quite neutral, but very natural and effortless sounding. More air, larger soundstage, more 3D, more resolving, more nuanced and subtle, more likely to fool me into thinking things are real. On the mellower side of things but not too laid-back. Never particularly harsh, but not dull either. HD650 is pulling out things I didn't think it would be able to before.

My only complaint is that in my very limited experience with tubes, some can really give the Senns balls (i.e. bass slam). The Teles are not those tubes. Really wish they had some more bass slam but are beautiful sounding otherwise.