Leebob – I believe such a dual pedal is possible. But, TBH, considering there a total of 5 cap values and 1 resistor value to change, doing so in a live circuit holds a considerable potential for a loud “pop” when switching. The only means I can think of to avoid such a “pop” would be to use a 6P2T MBB (make-before-break) switch. I’m sure such a switch is available, but will likely be costly and require a bit more enclosure real estate for housing. Just something to consider.
Personally, if I desired to have both the “Vibe” and a “Dr Phybes’, I would build two separate pedals – each with all mods available. I might consider putting them both in one 1590DD enclosure, (although they might fit into a 1590XX), possibly with an order switching option. But that’s just me. (And Barry does have quad matched phaser FET sets on sale right now. Dunno if he has any left or how long it will last.)
Barry – thanks for the bit of history lesson.