With a massive plate dissipation of 60 watts, the Tung-Sol KT120 is one of the most powerful octal beam tetrodes ever produced.
According to the manufacturer, "When used at the parameters found in existing 6550/KT88/KT90 circuits, the Tung-Sol KT120 is impervious to overload, delivering peak power with extreme reliability and long tube life. Taking advantage of the higher current handling capacity of these tubes, a very unique and super powerful and stable amp can be designed.” No kidding.
And, as an option, the Silver Seven 900 can be ordered with Tung-Sol’s ultimate mega-tetrode, the KT150. Its glass envelope is a special egg-shaped balloon that was developed to improve thermal dissipation and maintain a superior vacuum for the best sound.
Posts on various forums suggest that it may be even punchier in the top and bottom end than the KT120s. If that’s possible.