Mu-Tron PS-1

“Designed specifically for us with Mu-tron III, making batteries unnecessary. Comes complete with permanent cords and plugs for line current and Mu-tron III. Dimensions: 4″ long, 2 3/4″ wide, 2 1/4″ high. Finished to complement Mu-tron III. Operates on 110-120 volts AC, 60 Hz. Rated output: ±9 V at 30 mA maximum. Power consumption: 1 VA.”

– From original Musitronics PS-1 ad circa 1970s