About Big Muff Pi and “true bypass”. I’ve had an older version of the Pi (switch with 6 lungs) for a few years and it effected the bypassed tone a great deal: the sound was muddier and it cut the highs significantly, seemed to “eat the sound” so to speak. This problem occurred with a 9V battery and with adapter.
So… I bought the latest version of the Muff Pi (the one that should be “true bypass” according to EHX). Well, it’s not. It also cuts the highs, but doesn’t eat the sound nearly as much as the older version.
I have lot of pedals in my pedalboard, but all the testing was done with just a VOX ac 30, Fender Jazzmaster and the Muff.

The bottom line: This pedal effects the bypassed sound only that little that now I can deal with the muff being a part of my board. It’s a lot easier than dealing with no Big Muff at all…still love the sound of the pedal.