For replacement/substitute parts, see this forum topic
LadyAda ships with these replacements, with no noticeable sound differences
SubAtomic has done some analysis of these, and has found BA6110 to be only slightly different, yet perfectly acceptable (perhaps even more desireable: it produces the exact sound only a little louder, which can be a useful thing to slightly overdrive the mixer output for a little distortion)..
MomeRath reports that replacing these causes no sound difference:
Unverified (these may or may not sound the same, please do testing and post results!)
If you find other substitutions that still maintain the original sound, please post your results in the above format…