SS discrete amps are designed to avoid capacitors in the signal path, lots of feedback to minimize distortion (see Schiit's topology with the Magni+: "Topology: Fully discrete, fully complementary all-bipolar, symmetrical current-feedback design with driver stage and Vbe multiplier, no capacitors in the signal path and DC servo") while tubes are the opposite. OTL tube amps have capacitors in the signal path (except for Schiit Folkvangr) which imparts its own distortion characteristics to the sound