OK, so a day of frigging around with different stuff has lead me to a passive tone control for piezo. Some background: If you ever tried a normal guitar volume and tone setup on a passive piezo, you'll know the tone control doesn't work as it should. If anything, it acts more as a high pass filter than a low pass. This is because piezos have massive impedance compared to magnetic pickups. I usually use an active preamp circuit based on the Tillman design and that means I can put normal volume and tone controls after the preamp and they work as they should. But I've had a couple of commissions recently from people who will rarely plug into an amp anyway, so that brought me back to the search for a passive tone control that will work for a piezo. It's seems a bit silly to put a really good preamp in a gat that will rarely get plugged in. I tried a bunch of stuff I had read about with RCL filters but none of it worked, really, despite what some dude claimed. I suspect that, as usual,…