Per 'ABE' Abrahamsen in Mojo Blues
In 1972 Dr. Otala and Dr. Lohstroh finished their work in analysing transistor amplifiers to determine what actully created the "transistor sound" in general transistorised designs. The results of their innovative design work were incorporated in the legendary 25 watt amplifier. This product was the first commercial transistor amplifier to use this new design approach, and the amplifier was immediately recognised as dramatically more musical sounding than any other transistor amplifier. The same design philosophy, has been constantly updated by additional research and development.
After the 25 watt amplifier had established a new standard for transistor amplifiers, research was undertaken to find ways to make the amplifier even better, and to extend its highly musical sound quality to more powerful amplifier designs.