Old School features a fast/slow toggle switch greatly extends the range of speeds available, and the WAVE control transforms it from a smooth vintage tremolo to a choppier rhythmic tremolo. Finally, there is a switch to double the power for more headroom without needing a separate 18V power supply.
The Old School now features an even higher voltage charge pump that takes 9V & converts it to over 20V...and 15V into almost 40V! The higher voltages yield more headroom & a more open & smooth feel to the tremolo circuit. This charge pump has no impact on the LFO section, so the smooth tremolo effect is not impacted by the LO-HI power switch.
Speed: Controls the speed of the tremolo effect.
Depth: Controls the depth of the tremolo effect.
Level: Controls the overall output of the Old School tremolo.
Wave: This control transforms the tremolo from a vintage sine-wave tremolo to a choppy, modern square-wave style effect. Turning it clockwise makes the tremolo effect choppier, but also reduces headroom & adds some distortion. CRACKLE OKAY!
Power: This switches between the normal power source (typically 9V, but can be powered up to 15V), and a charge pump circuit that increases the voltage by about 2.3 times. The HI setting has more headroom & less distortion, especially when you turn the WAVE control clockwise.
Range: This controls the range of the the SPEED knob. The original circuit had a very limited speed range, and this control extends the range much wider, both faster & slower than you will ever need.