It's still a bit early for me to be totally comfortable with the new Ampersand, but after spending a long time comparing it with my Less BX2, I was surprised that a much smaller unit as the Ampersand was giving very comparable sound quality results, and even be a bit more powerful
Now I am spending for a few days some more hours to compare my target "on the way" combo which is intended to be the "Sony WM1A (Low Gain) + Ampersand" + Vision Ears EXT or DCA Stealth against my already impressive but still a bit too bulky FIIO M17 + DC12V3A Powerbank for enhanced audio mode.
I am listening some nice Hires tracks coming from some DSD like Hiromi Hueara / Manu Katché or hires flac from Ibrahim Maalouf ...
Again, I am impressed that such a small Amp unit can really be comparable to a FIIO M17 even connected to an external power unit of 12V/3A.
Last August, after mgoodman said, they needed to rework a bit the design of their Ampersand, as it was really falling short with DCA Planars (Noire), so from that annopucement, I was not expecting anymore that this amp would provide enough power with low impedance and low sensitivity Headphones. So these last ten days, are really a surprise to drive so nicely the 23 Ohms 92db of the DCA Stealth ...
Till now, I was thinking the Less Bx2+ and Fiio M17 were probably the only more or less portable units able to drive the DCA Stealth and HEDDphone One => clearly the Ampersand can manage it very well too.
For people who do appreciate, like I do, the Sony WM1A with some custom firmware (MrWalkman), it can be directly plugged with the 4.4mm in low gain to the Ampersand and drive the DCA Stealth with an impressive sound quality from ultra low frequencies to high frequencies. It can even work in an enhanced mode for CD quality with some DSP DSEE-AI.. with no hiss at all or any harshness ...
Then on the way, when I am no more in a plane train or hotel, I just unplug the Ampersand and DCA Stealth from the WM1A and I switch to a Vision Ears EXT or Sennheiser IE900 to be plugged to the 4.4mm output (High Gain) and I can walk in the street be in the bus/underground with the WM1A in my shirt pocket and IEM in my ears, which is much more difficult with the bulky FIIO M17.
I would already say, even if I need some more weeks/months to discover fully the Ampersand, that at least, it's worth to give a real try to this amp for people who need a portable solution beside their usual pocketable DAP to drive most of the difficult headphones to drive .... worth to do