This stereo amplifier offers superb musical clarity and plenty of power in one compact chassis. Utilizing the finest quality parts, and entirely hand built by experienced craftsmen, the ST-150 is VTL’s offering of a high value, high power stereo tube amplifier. The noted VTL quick, clean, musical sound and exceptional bass punch is delivered here by the 6550 tubes. Exceptionally well suited to triode operation, yet they are also very dynamic and fast in tetrode mode, these VTL amplifiers are well-suited to smaller electrostatic panels and dynamic speakers not requiring high current. For commanding performances on the midrange and clarity on the top, VTL wins hands down. In triode mode, the amp is best suited to speakers with an efficiency of 92dB/1W/1m or higher.