For subjective impressions, read here: https://www.superbestaudiofriends.o...a-headphone-amp-reviews-and-discussion.11513/ NOTE: Measurements below use different parameters than other sites, so not directly comparable. I'll be posting these measurements throughout the day. We also use output levels (0dBu/0.775Vrms) which is lower than some other sites. These output levels are still extremely loud, but more reflective of peak volume levels to be expected with very loud listening. Singxer SA-1 Headphone Amp 1kHz steady state sine 0dBu output (~100db SPL from Sennheiser HD650) 300-ohm load from SE (phono jack) output, BAL in 64kFFT Singxer SA-1 Headphone Amp 1kHz steady state sine -10dBu output (~90db SPL from Sennheiser HD650) 300-ohm load from SE output, BAL in 64kFFT Let's try lower 33ohm ortho / low-impedance loads next.