Info from the manufacturer about the original:
The Direct Drive provides guitar players with classic amp tones!
True to life overdrive with greatly reduced compression artifacts, this unit has it all, clarity, great guitar volume knob control, solid punchy articulate bass, gain range from a little juice to fat harmonic overdrive. Give your guitar playing a vintage voice with this stellar performer!
Internal bass control- The Direct Drive can dial in a stronger deeper bass response to perfectly match amplifiers.
Adjustable presence circuit- The internal presence circuit allows the Direct Drive excellent clarity while limiting fizzy artifacts.
Volume knob response circuitry-more shades and textures at your fingertips just by adjusting your volume knob.
Low compression artifacts!-By carefully tuning the Direct Drive compression has been reduced to the most amp like response to date!!
Three knob control for tonal versatility-The Direct drive uses a simple three knob control layout with a push/pull tone knob for a second Fat Harmonics voice. With the Tone control pushed in the Direct Drive brings the classic tones of the past to veteran players then simply pull the tone knob for modern fat harmonic tones...KILLER! High quality components- Players have requested the use of carbon resistors, metalized polyester caps Elna silk particulate audio caps. These components were thought to be only available on the highest priced pedals. Players asked, and we deliver...no problem, no exaggerated "boutique builder" pricing.
Ready for 18 volt operation-The Direct Drive operates from 9 volts to 18 volts, this allows use of higher voltage converters and supplies, for players who want to try higher voltage tweaks.
Barber adjustable phono style recovery stage- Most of our op-amp based overdrive pedals use a cool old style phonograph circuit to recover the frequencies lost in the overdrive stage, this worked great for vinyl and now works great for guitar overdrive!