first,i want to thank Alex for posting his layout. IMO, I think the parametric mids Q and Freq controls were meant to be external pots (which makes it way more flexible).
NEW LAYOUT FOR THE PARAMETRIC WITH CORRECTIONS IN NEW POST BELOWI also drew up the simpler, 'stock' version without a charge pump and with selectable mids for those that don't want the parametric# if you want to run it on 18V from a 9V supply, just build and add a tiny daughter board for a charge pump# I haven't built and verified it yet, but I've gone over it a zillion times so I believe that it is correct# this one will fit in a 1590B even with the charge pump: