I remember the thread. It wasn't based on much concrete evidence, other than Frank confirming that the preamp (i.e. op-amp chip) did appear to change slightly sometime in recent history. We know that EOL for the original EMG op-amp occurred in late 2018, so it's unlikely that EMG stopped using them anytime before 2019 or even 2020 depending on how much stock they had on hand when the chip was discontinued.
Also, I don't recall you comparing newer vs older 81 models, only 57/66, etc.:dunno: