Hi everyone
once I’ve found this info about the Moog Source on the web:
Spoinky basses - patches with filter resonance turned up while the filter cutoff is spiked with an EG with fast decay to zero sustain - aren’t quite the same on the Source because the resonance on the Minimoog filter is nonlinear. “Nonlinear” means the resonance on a Minimoog filter does not stay constant across the full frequency cutoff range - it disappears as the filter cutoff falls to low frequencies. So when a “spoinky” bass is dialed up on a Minimoog, the filter resonance disappears as the EQ sweeps the filter toward low cutoff - the net effect is the bass sound is full sounding.
Moog subsequently viewed this nonlinear resonance as an engineering “fault” and corrected it in new designs - including the Source. So the resonance on the Source filter stays constant across its full cutoff frequency range and the engineers were happy. But this was also why later Moog instruments also didn’t sound like a Minimoog and the customers were not happy. Moog went through a lot of head scratching to find out why and never realized that their “correction” was the source of the difference.
I think this happens to Moog Prodigy and Moog Rogue too, right?
If so, I’d like to know if it is possible to modify the Prodigy (model above 4160) to behave more like the Minimoog. I’m skilled with solder iron, I just need to understand which part/parts are responsable for this fix they did.
thank you
Easiest solution: get a Minimoog D. 
Because I don’t believe that this is the only thing contributing to the “Minimoog” sound.
And since there are many, many variations of the implementation of the Moog ladder filter circuit, trying to recreate the behavior of the one inside a Mini would not be a simple task in other machines… 
Thank you for the reply
But your approach seems to be too much mystical (and not easy too 
).
Seriously, from a techincal point of view, there is nothing special about minimoog filter schematic, and so I can’t see any reason why a prodigy can’t sound like it, once it is modified to remove that fix as explained in the quote above.
I just need to understand what the fix was
If the goal is only to get a filter behavior similar to the one in a Mini, then it could be possible to get close to it, I guess.
But as to getting the sound of a Minimoog D out of a Prodigy, MG-1, Rogue, simply by modding their filter, I’m not convinced.
Only the Source, which has oscillators that are “beefy” enough to approach a Mini, could maybe benefit from such a filter mod.
Remember that much of the “sound of a Minimoog D” comes from a series of engineering miscalculations, analog circuitry quirks and erratic behavior and varying parts tolerances from machine to machine, and minimalist design in some parts, which were mostly corrected in subsequent designs over the years in other models from Moog but at the cost of loosing some “character” sometimes.
It’s fairly agreed, amongst musicians and vintage Moog aficionados, that the only Moog that comes really close to the sounds of a Mini is the Moog The Source.