Pete Cornish has been at the helm of the stompbox production queue with clientele ranginf from Lou Reed to Noel Gallagher and David Gilmour of Pink Floyd. The SS-2 is now discontinued and has been replaced with the SS-3. However the SS-2 remains a solid favourite and it looks like it's circuit secret is out and about.
Here's a demo video of the Cornish SS-2 in action (Versus the Gearmandude's [I swear this guy is Jack Black!) own 808 remake. I actually prefer the sound of the Luther Drive here...):
The Top Tone Light Drive is a straight circuit clone of the SS-2 and MWichini of the freestompboxes forum has produced this schematic of the unit:
[NOTE - The tracing of this pedal is still in progress - check out the link to the freestompboxes forum topic to check it's progress!]
"The input to this unique device is our universally acclaimed High Impedance, Unity Gain, Class A, Buffer Preamp with it's superior RFI rejecting capability (to eliminate Radio Station interference) and Low Impedance Audio output, allowing the use of extended cable runs from the SS-3™ in bypass mode. The fixed High Impedance load presented to the Guitar allows the pickups to operate at their optimum, even when several effects units are connected after the SS-3™. The Unity Gain Buffer also prevents "Ghost Distortion" being audible in Bypass Mode. Our effects get the most benefit from being fed into a clean, full frequency response amplifier and I recommend that when you receive your pedal you connect it up without anything else in line, just Guitar/Pedal/Amp, and discover the way the controls interact, both with themselves and the guitar/amp controls. Adding the rest of your effects, you may find that you need to make slight adjustments to these to compliment the constant signal provided by the SS-3™."
However, we've got a schematic for that too, here it is:
So basically what you've got to do is run one of those buffer circuits in front of the Light Drive circuit and you've got an SS-2.
Personally I'm not a fan of the sound of the SS-2 but I guess David Gilmour has more say on tone than myself, just ;-)
Here is the on going thread on freestompboxes.org: http://freestompboxes.org/viewtopic.php?f=7&t=16071