Just for the sake of amusement, I built something similar to this, but with a 4066 to select the type of clipping, and a couple of gyrators for the tone controls. I was pleasantly surprised by the results. The IC line-up is a 4558 for the clipper part, a TL074 for the input and output buffers and the two gyrators, two 4066s - one for bypass and the other for clipping selection and a 4013 for the bypass on / off. It's a neat, small PCB, and appears to be mostly full of ICs! All the controls are 500k and 50k linear with tapering resistors where required.
I suppose I should put it in an expensive box, thoroughly goop it, and sell it at some exorbitant price as the "ultimate" boutique device! The boobs at TGP will fall over themselves praising what is - essentially - just another Tube Screamer!
"Why is it humming?" "Because it doesn't know the words!"