Part 2 (of 3) of Storm Tide schematics is online: http://home.debitel.net/user/jhaible/jh_storm_tide_flanger.html Take a look at U2 - it's a single opamp 24dB/oct filter. Does not work with other opamps like TL071 or LF351. If you find an error in the schemos, please mail me. JH.