Comments on the Twinhead as an OTL headphone amp on this board has been outstanding, at least when it works.
I got to home audition one.
I didn't try the OTL headphone amp because what I was looking for was just a preamp (I already have an XCans v2 w/ Mullard 6922 gold pins & X-PSU). I really wanted to like the Twinhead because I can lessen clutter (sell off the X-Cans/X-PSU), have remote on the volume pot, and most importantly, get into the sound of directly heated triodes (2A3!).
As far as midrange, small ensembles, laid back music goes, neither the a tricked out Foreplay nor a Conrad Johnson PV11 (w/ RAM 12AU7 and Audio Note/Infinicaps in the line stages). Sound was lucid, warm, lush, absolutely sweet and gratifying.
Problem was, no matter what CD I play, the sound was warm, lush, and laid back, even on livelier albums. Maybe more burn in and tube rolling was needed.
In the end, the more balanced presentation of the PV11 won my heart. It wasn't as lush as the Twinhead but it was still quite warm and lush but most standards. IT offered more detail, greater extension at the extremes, and good PRAT.
Since the PV11 was pre-owned and the Twinhead new, I could actually buy an MG Head OTL for the price difference!