I just noticed a potential problem with this preamp.... maybe someone can enlighten me.
With nothing plugged in, no buttons pushed to activate the tuner, this preamp is pulling .88ma from the battery. If you look at pic 3, you will see two pc boards. The top board is where I connected the external pots. I have disconnected that board from the bottom. The bottom board is where you connect the piezo pickup, connect the battery, and connect the output jack that has the switched ground. So everything except the battery is connected and I am seeing .88ma being drawn. I have two boards doing the same thing. Did I just happen to stumble upon two Grade 3 boards?