Incoming: Black Ross! How to power it??

[Heady Jam Fan]

What is so special about the circuit that nobody has been able to create a clone that is near indistinguishable from the originals?

Nothing. I think there are good, accurate clones. But they still don't sound the same. Could be:
- Age of the pedal / components
- Different manufacturers for the components, thus the components differ slightly in clones.

Think about this:
- A new TS even with the same circuit and spec sounds different than a vintage TS.
- A new TS from another company other than Ibanez, even with the same circuit, sounds different than a new Ibanez TS.

IMO, cloning only goes so far to match the original (of course that depends how closely your listening). Doesn't mean clones are bad. I prefer the original because, well, its just kinda cool. And in this case I think it sounds better. Not to mention, a Black Ross costs the same (or less than) most clones. Having said that, I would be happy using the Analogman or Retro Sonic.