I just wanted to give a little update on my HD700 Balanced / PONO "ecosystem." Before anyone says that I'm polluting my "ecosystem" by using HD700s (as HD700s seem to have a notorious 7k treble spike), there's something to be said for why I wound up being someone who is still enamored with this combo long after the PONO fanfare has waned a bit and the HD700 has become the Grado-cum-posterchild for "burning headphones at the stake". I've found that because the PONO is dead neutral (ie: not dark / bassy nor particularly bright), it melds well with the HD700 and a balanced Black Dragon cable. The Balanced cable, combined with PONO's balanced mode, helps to send more firepower up to the headphones; single-ended the HD700s are a bit hard for the PONO to power at anything less than 45 to 50% volume. The copper (and much thicker copper AWG at that) helps tame the treble a bit; the stock SPC cable is a bit too strident for long-term listening. Would I say it's a "reference" setup end to end (ie: if I had HD800 instead)? No. It's still got a bit of a bass-oriented mindset, and it still has its "SennHammer" tonality, but being able to get a fully immersive experience at 25 to 30% instead of 45 to 55% (and a fuller, fatter, richer, yet not flubby or bassy experience) is something that I'm truly enjoying.
2-plus years with the PONO and the only way I would replace my PONO is with another PONO, or with a PONO2 (if one ever comes out, and assuming it's as good as this PONO)