The M-120 is marked by an exceptional design that places it squarely at the forefront of tube technology. Just a few of the notable features are a "slow start" logical turn-on for extended tube life, a massive high capacity power supply, and the ability to operate in either ultra-linear or pure triode mode. Other refinements include mechanically isolated transformers, matched octets of 6550/KT88 tubes, and separate 4 and 8 ohm taps on the rear.