Page "Mesa Boogie" Paragraph 8

The real breakthrough came when Smith began building a preamp project for Lee Michaels to drive his new Crown DC-300 power amplifiers.

Not knowing what signal was required to drive the power amps, Smith added an extra tube gain stage to the preamp, with three variable gain controls at different points in the circuit.

In adding this extra gain stage, Smith had created the first high-gain amplifier.

He set about designing a guitar amplifier around the new principle, and in 1972 the Mark I was released.