I've done some searching, but aside from brief mentions there is no real explanation of the internal (bias?) trim pot on the PPB. I just got one used and did not get a manual with it, nor can i find a pdf verison. I'm wondering if anyone can give me insight into how this internal trim pot functions? In the couple days I've had the PPB, I tested the internal pot on the extreme ends. Fully counter clockwise it seems like the signal going into the pedal is much hotter. I can have the external boost knob around 9:00 or so and it seems to be at unity gain. Likewise, a little digging in gives me some serious grit and breakup, especially on the lower notes. Conversely, turning the internal pot all the way clockwise seems to really choke the signal coming into the pedal. When i do this the tone seems to warm up and round out a bit more, though I have to put the external volume knob past 12:00 to find unity gain. This seemed counter-intuitive, as I would expect more output and breakup as I turn the internal trim pot 360-degrees clockwise. I'm hoping to explore the middle range of that trim pot if I have time tonight, but I'd be curious if anyone can explain what's actually happening and how this internal adjustment is meant to affect the tone and output of the PPB?