Designed to emulate the sine-based trem of the '50s, the Mad Professor Mellow Yellow Tremolo comes as both hand-wired and BIF Design models. Letting you dial in soft, swinging tremolo or deeper modulation, the Mellow Yellow is calibrated for symmetrical modulation using a sinusoidal oscillator just like many vintage amps. Its highly playable and musical trem can fit essentially anywhere in a setup, blending wonderfully with clean and dirty tones.