Audio Research REF75SE Stereo Tube Power Amplifier75 watts per channel from two KT150 output tubes per side Audio Research's Special Edition revision of the REF75, which replaced the KT120 tubes of the original with the larger KT150, one of the most capable beam tetrodes currently in production. The SE designation goes beyond the tube swap: upgraded internal components, improved power supply regulation, and the circuit refinements Audio Research applies when the baseline design is already at