Mad Professor Golden Cello This is an overdrive with a tape echo-type delay function. The delay turns off when set to zero. The delay time can be adjusted with the mini-knob on the circuit board. It can be powered by 9V to 12V. It produces a smooth distortion, like a violin or cello. I think it's suitable for solo phrases, blues, etc. This is from the Rep International era, and there aren't many of these units in Japan. There are scratches on the side.