The 1310 Analog Harmonic Tremolo is an analog stompbox designed to recreate two of the most desirable vacuum-tube based modulation effects found in American amplifiers of the 1960s. The Supro 1310 Analog Harmonic Tremolo pedal’s AMPLITUDE/HARMONIC switch allows the musician to choose between these distinctly different, vintage effects. AMPLITUDE mode provides the traditional swampy, tremolo sounds generated by bias modulating the power tubes in the original Supro amps. HARMONIC mode provides the psychedelic tones of Leo Fender’s brownface and blonde amps from the early '60s. Supro has implemented Leo’s unique 'harmonic tremolo' effect within the output stage of the pedal to create an 'amp-like' modulation experience. The Supro 1310 Analog Harmonic Tremolo pedal features preamp and power amp sections, with an actual output transformer deployed to recreate the magnetic saturation and coloration of the original vacuum tube based effects found in these historic amps. Along with the standard modulation controls for speed and depth, the Supro 1310 Analog Harmonic Tremolo also features a gain circuit that allows the musician to overdrive the output stage, right where the modulation effects are created. The GAIN control sets the amount of 'preamp' gain in the pedal. As you turn the gain up, the 'power amp' circuit will gradually be pushed into overdrive. This control gives you a wide range of sounds from clean to grind, with magnetic saturation occurring as the power section is pushed into overdrive. As you crank up the gain, the overall output level of the Supro 1310 Analog Harmonic Tremolo is automatically compensated in order to maintain consistent signal level. This allows the musician to use the GAIN control to alter the te