The HA-300MK2 is a Class A Transformer-coupled headphone and speaker Single-ended Triode Amplifier (SETA). It uses 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, thats why it is referred to as SETA, and then feed to a pair of output transformers for single-ended headphones, XLR-4 and 4.4mm balanced headphone output, and one set of speaker terminals.