Ive had this saved on my desktop for a while but i can't remember who to credit for it. I vaguely remember saving it because someone had fixed the previously available schematic and successfully built it. Unfortunately I'm not smart enough to transfer it onto veroboard
I have a layout of this thing but it'st based on the original schematic. I just needed to swap two resistor values to make it work properly (I think). The layout is verified and sounds pretty effing good. I'll post it tomorrow if you are interested.