The HA-300MK2 is a Class A Transformer-coupled headphone and speaker Single-ended Triode Amplifier (SETA). It use a matched pair 300B Direct Heated Triode as output tube and a matched pair of 6SN7 as driver tube. The tube amplification circuit is operated in Single-ended, that’s why it is referred as SETA, and then feed to a pair of output transformer for single-ended headphone, XLR-4 and 4.4mm balanced headphone output and one set of speaker terminal.