Fuzz King
The Fuzz King is a very important fuzzbox. It was used by me, and nobody else I have ever heard of. How cool is that? It is a FZ-1a variant with fixed bias and a gain control on Q2. It is utter garbage, since the 3k3 resistor on Q3 pulls the base bias voltage down too much. The gating makes it very hard to use. But, if you disconnect one end of the 3k3, you get a cleanish boost turning into a mild sustainey fizzy fuzz which is loud and will overdrive a tube amp well.
So I think this is the kind of thing the Yardbirds would have liked, it gets you an overdriven sound at any volume and cleans up with the volume control