I built the single channel version of this with a Russian MP20 Ge transistor and it works beautifully and is a favourite pedal when used as a booster into a low-gain OD. I generally only use low gain OD. Using this as a boost gives me that old-school warmth and sounds almost like a treble booster - the fattest, warmest, quietest treble booster of all time. I swap between it and a TI Boost (Dark Esbat) - both are excellent.
But I've had a lot of trouble with the dual version. The first one worked ok but I used a 3-way gain switch by mistake which made for some strange sounds. Then the second one I built I was painstakingly careful but get no sound at all. For the life of me I can't work out why.
I have one PCB left...