So I came across this which appears to be the schematics for a wal pro bass preamp, quite similar to a normal wal preamp if I remember correctly, well, outside of the whole filter thing. Pulling out the pickup knobs functions differently too. What I am curious about is the circled part, which appears to be the switchable pick attack function. Having no clue how to interpret a schematic as it relates to tone, is there a way to determine the approx frequency the pick attack is spiking from that schem? 330k resistor into a 2.2n capacitor....if I'm reading that right. Thanks.