This pedal out of so many overdrives seems to work best with my amp, vox ac30
but I have some issues with it, namely the buffer and some tonal tweaks I would like to make
what is the SD1 circuit a copy of?  what are SD1 clones or similiar style pedals. 

It's not a copy of anything.

Build/buy a Tubescreamer.

Read www.geofex.com.

Build/buy a treble booster for your AC30.

  Tubescreamer
  SD-1
  Bluesdriver
  All have gain, tone and volume controls
  these are just a few of the Opamp feedback loop clippers...you recognize this type of clipping generation by the diodes in the feedback loop of opamps, used for clipping the signal.
 

Boss SD-1 is a development of their "OD-1" which was one of the first
"op-amp" with diode clippers, from the late '70's ( '77 - '78  I think )
It's not a million miles from a TS-9 but uses asymmetrical clipping,
where the Ibanez is symmetrical ( one diode in each direction )
They each have patents in these "versions" of clipping a signal

TS-9 well worth trying, as is an MXR distortion + or one of the original
"Black box"  Marshall series, like a "Blues breaker" or "Guv nor" which
use LED's for clipping.

Marty.