Tsakiridis Artemis mono blocks these are some of best tube amps I have ever owned dead quiet amps. Amps are pentode triode with a flip of a switch. Pentode 35 watt ( EL34 ) / 45 watt (6550) Triode 20 watt ( EL 34 ) 28 watt ( 6550 ) adjustable bias just recently installed new tubes and re - bias. Matched quad of Russian Mullard EL34 and matched quad of Genelex 12 AT 7 only reason for sale trying to downsize as I have a lot of audio gear. Local pick up only no shipping