Apologies if I already posted the guts of this earlier, but this has to be my all-time favourite build, this is a PHENOMENAL pedal! So happy with it, a massive range of overdrives from it, and with cap switching it can be used for either bass of lead. From blues crunch to heavy distortion and fat squashy fuzz, it's all here by the bucket. Such a lot of fun! Here's the insides:
This is the clipping section - wired to a 6-way rotary switch, enables you to choose between 6 different diode clipping modes, asymmetric modes, different pairs, Ge/Si mix, LED's, smoothing capacitor, each has a different overdrive character and gain range
Add to this two switchable input caps for bass or lead, the low freq setting adds a massive fat bass tone or switch it to lead for the classic tubescreamer mid boost sound.
"The best way to do it...is to do it." - Amelia Ehrhard
Flateric (aka Al Heeley) appears not to have been online here since November 2012, so I wouldn't hold your breath of getting a reply from him. I've done a little homework for you, and will post what I found here for anyone else who might like to have it all in one place or contribute.
Flateric based this design off of MarkM's layout of a TS-808 as seen here.
If you read through this thread, you can see how Flateric/Al inserted his mod into the 808 layout. Removing diodes 1 and 2, and capacitor 4. Check specifically post #24.
See this Nuts2 thread for discussion on the clipping module.
If you check this thread out, Flateric simplifies his clipper module back down to 3 options vs. the 6 based on what he finds useful. I've built a few of these now and gone back to a mini 3-way toggle switch as only 3 of the diode combinations are significantly different enough for me. I go for: 1) red led pair 2) one Si and one Ge diode 3) asymmetric 3 Si diodes (4148 or similar) Not found the smoothing cap to make much difference that cannot be covered by gain/vol pot settings, I love having the input cap switch giving a HUGE bass boost if you want to use it, gives a glorious thick guitar overdrive or makes it brilliant as bass distortion unit.