Just got mine this morning with the ESS Card. Very interesting amp, never really heard anything like it. Just my impressions off the internal DAC but It almost sounds like you have a DSP-like effect or slight reverb applied lightly to the sound. Vocals come across very ethereal, like they’re singing right in my ear. Separation is very, very good. Note decay is very quick, very nice for pop and EDM. It’s definitely the most ”tube-like” solid state I’ve heard save for my old 70s McIntosh 2505. Everything other amp I’ve heard claiming tube-like qualities but a pale imitation. This is its best selling point IMO is a true tubey sound without the hassle and heat of bulbs. I imagine the ASR guys would have a meltdown poking and prodding it lol.
I will say it’s one weakness is it can get a bit fatiguing, it’s very dynamic and sharp but I’d attribute it to the Sigma dac, I’ve never heard one that isn’t. Will have to try it later with an external R2R.