I came across this mod to the Big Muff, using two pairs of three 1N270s connected in series (one forwards, one backwards) as opposed to two 1N4148s, connected similarly. The forward voltages compare favourably (Ge = 0.692V, Si = 0.605V). Result? A vintage BM Ge dark and smooth sound, and a somewhat brighter, ‘fizzier’-sounding Silicon alternative, with no appreciable drop in volume when using one of Barry’s DPDT switches (pictured).