the older ones (i.e. not the reissues) sound better because they use the LM308 opamp which is now rediculously hard to find - I found one in my local electrical shop but nothing anywhere else (even on the net).
you can try all the usual mods that you can do with opamp distortion circuits - different configurations of silicon & germanium diodes or LEDs either after the opamp's output and/or in the feedback loop.
increase the gain pot's value for more gain, change cap values to EQ the circuit to taste - the first cap in the signal chain always has a noticeable effect on the tone.
it's hard to say what mods to try since you weren't very specific - is the gain too low? farty bass? buzzy treble? not enough mids?
:twisted:
