Mosvalve/Bk Butler RT-2100R rack mount amp. 100 watts of power. Fantastic clean and overdrive tones. High quality US made amp at a great price point. Used but good overall shape.. Some crackle in the volume knobs, most likely just dirty pots, evens out, only crackles when moving the knob. Has 2 brand new 12ax7 preamp tubes. Have 2 more Mesa preamp tubes I’ll send with it so you can dial in your preference. The Tube Works Mosvalve RT2100 is a vintage rack preamp power amplifier that was made in the United States. Known for being hard to find, this model is part of the Tube Works brand and features a unique tube-driven design.