by FrankH » Wed Jun 20, 2012 7:01 pm
The main problem with any op amp swap out (besides the possibility of lifting/damaging traces) is the components surrounding the chip. A good design optimizes the values of the various resistors and caps directly attached to the chip.
(I'm pretty sure Cal Perkins, a superlative op amp tweakhead, did the final preamp design). Substituting another chip may not play well with these components and in some cases may degrade the performance.
That said, please note that all the surrounding components are surface mounted and are a bitch to replace. I might suggest working with one mic pre by replacing the op amp with a socket and experimenting with substitute chips before going whole hog into a complete chipectomy.