I also invested in a Cracky as an investment in the Senn HD650 (in the guise of the Drop x Senn HD6XX; and I have a very nice pair of original Senn HD580 Precisions tucked away). Glad I did. When, a while ago, I wanted to take the turn from two-channel audio to try headphone audio, I got the Senn HD580 Precisions - and didn't enjoy them all. After my decades of two-channel experience, through the Senn 580 someone through a huge blanket over everything after stuffing cotton in my ears. I had a number of nice DACs for the period, with the "best" headphone amplifier I was able to use then was a Millett Hybrid tube amp.
Undaunted, or foolhardy, more recently with so much more headphone kit available now I gave it another go. Massdrop Senn 6XXs with a mix of other DACs and amps and I've found the experience better. I decided to probe for myself the reputation of the Crack/Senn combo (I was already familiar with other Bottlehead gear, so the reputation preceded my Crack adventure). Fun, fun, and FUN! There's a "sound" there, for sure, and it's just a lovely thing. And it has been more than just the sonic experience that I've enjoyed. The Crack is just a lovely, elegant, characterful thing to have and to use.
I have wanted to get all my other headphones, non-low impedance headphones, in the Bottlehead game, too, so I did get an S3X and have started building it. Unfortunately, life has been interrupting progress, but it will get done soon enough, and with the requisite care to do it properly.
I have a question about using other high impedance headphones with the Crack. Beyers, AKGs, and other Sennheiser models... I haven't listened to many of these, mostly being dissuaded by the comments of others. Largely, I get the sense of many models being bright - too bright to the point of being harsh and mediocre bass performance. BUT, this is where I have an inquiry about how these headphones might fare with the Crack. I haven't seen many comment on pairings with tube amps, and specifically with the Crack.
How would people characterize their experience with other high impedance headphones, other than the Senn 580/600 family? I am most specifically curious about peoples' take on the Sennheiser HD800S with the Crack, but I am also curious about how other high impedance headphones work with the Crack.