The old RAT pedal uses an LM308 opamp. But I couldn’t find any genuine ones. So I did an experiment with LM301 and OP07 opamps. I think the later RATs use the OP07.
I built a RAT clone (http://tagboardeffects.blogspot.com/2012/01/proco-rat.html) and ordered some LM301s from Tayda and tried the following:
– OP07 (no compensation cap)
– LM301 with 100pf compensation cap
– LM301 with 33pf compensation cap
I know it’s subjective but, for me, the last option won. Sounded a bit grittier.
(BTW – the Tayda LM301s are genuine as they squeal like a pig without the cap unlike the “LM308” I bought off eBay which was a repainted OP07)