Boss SD-1 mod Help!

[Slash1]

My SD-1 doesn't sound as good as another pedal that I have that's based off an SD-1, the other pedal has a warmer and more organic tone and "feel" and the SD-1 just feels and sounds a little lifeless compared to it.

Are there mods for the SD-1 that will make it sound warmer and more organic? And if so what part of the pedal should I focus on modding, the chip? the diodes? caps?

(Not looking to add gain or volume or even alter the eq)

[Mark Hammer]

Never underestimate the role that component tolerances, especially capacitors, play in why some pedals sound the way they do.
 
Consider adding some capacitance in parallel with the 47pf cap in the feedback loop of the clipping stage.  And if there isn't such a cap already there, add one.  In that location, capacitors roll off more high end the higher the gain is set for.  At min gain, a 100pf cap in the feedback loop won't roll off highs until well above human hearing range, but at max gain, it will roll off starting around 1.6khz.  That may sound unreasonably low, but remember the roll off is shallow, and that the clipping will add plenty  of high end.  But that additional harmonic content will be multiples of the notes you're playing, NOT multiples of the harmonics of the notes being played.

The other potential culprit is the .047uf cap from the inverting pin of that clipping stage.  This sets the low end rolloff, in conjunction with the 4k7 resistor, at around 720hz.  That assumes the cap is exactly the .047uf it says it is, and is not actually less than that.  Consider beefing up the low end a bit by either replacing it with a higher value (e.g., .1uf) or tacking on small values in parallel until you hit the tone that pleases you.