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I loaded up my 1983 TS9 (with the 2 resistor changes to make it a TS808) with 11 different chips. I recorded them, too!
Strat->TS9->homemade JTM45 style amp->Shure 545SD -> Symmetrix Mic Pre -> Soundblaster 16 (ahh, the weak link sorry about the hiss!)
It was really hard to tell the better chips apart. I'm going to provide my listening notes with the lURL for the clips because it's extremely difficult to hear the differences in the clips! Even while playing and listening, we're talking about splitting hairs... There were a few that had some extra harmonic goodness, though.
http://www.theinside.net/misc/ChipsKorean 4558 (scrounged out of an old Symmetrix Gate) - pretty raunchy, has a nice midrange harmonic content, good gain
JRC 4558 (the stock, holy grail chip) - a bit better than the Korean, nice midrange harmonic content, good gain, some raunch
TI RC4558P (the "other" stock TS808 chip)- Got some swirl, good midrange, nice gain sound, less ragged than the JRC4558
TA75558P (dreaded stock TS9 chip) bright and boxy, gargled transients, not the worst, though - typical stompbox sound, kind of fuzzy
TI TL072CP - less gain/volume, slightly cleaner, perhaps more natural sounding, doesn't have the push in the mids. Blander
TI NE 5532AP - less, less, less real typical pedal sound, blander. Yawn...
LF 353N - Oh yeah, nice harmonics like the TI RC4558P, perhaps a bit leaner, a little extra something in the attack...a good one!
ST TL072CN - Really balanced, clarity, warmth, and gain. Very clear, revealing, bright, bell-like attack. Might be good if your amp is really pushed. Doesn't have as much motion to the sound. Better than the 5532AP.
NE 5532P Malaysia - better than the 5532AP, sounds kind of gargled when you hit it hard, good gain, boxy sound
Burr Brown OPA2134PA - Bland, bright, sterile - gargled, grainy kind of distortion. No harmonics...move on...
ST LM833N - Raunchy, but clear & warm, not much swirl or harmonics, good for crunchy rhythm, articulate leads - perhaps a bit less compressed?
Ahhh...I'll never get those 2 hours back!! Waste of time, perhaps....