Hot Chocolate Envelope Follower and Filter

Built for Tim Gane
I don’t build so many pedals anymore as the tubes have taken over my life mostly!  That said, this circuit has always been one of my favorites.  It uses a very standard, textbook state variable filter and a pair of vactrols to create the classic “bwah bwah” auto-wah sound.  In fact, in all ways it is essentially a Mutron 3 just with a few added features:  all three filters are brought out on separate volume pots for more sophisticated eq; the range of the sweep and intensity can be dialed in; and it runs off a +/-15 Volt power supply for better headroom.