In the early 70’s there were several Japanese companies copying and altering Big Muff circuits.
One company, Ktayama Electric Instruments Co., came out with their version of the Big Muff called the Mirano EF-1 Exciting Fuzz.
The Exciting Fuzz has a very sweet sound to it due to the low-gain transistors. The fuzz is punchy and warm yet still has a lot of gain. When you play chords, the fuzz cascades into each string while retaining a lot of clarity.
The tone sweep is very balanced and even in the lows and highs.
The Exciting Fuzz uses NOS BC109B transistors that are very similar to the low-gain transistors used in the original pedals.