magnetic cartridge amp:

click here to enlarge schematic

parts:

U1	LM387 integrated amplifier ic
R1	47k ohm resistor
R2, R6	100k ohm resistor
R3	240 ohm resistor
R4	2.4k ohm resistor
R5	1 megohm resistor
C1	1uF electrolytic capacitor
C2	33uF electrolytic capacitor
C3	0.003uf ceramic capacitor
C4	750pf ceramic capacitor

all resistors are 5 or 10 percent tolerance, 1/4-watt
all capacitors are 10 percent tolerance,
rated 35 volts or higher

a magnetic pickup from an old record player can make a great pressure, and vibration sensor. replace the needle with a plate of thin metal (copper off a pcb is good,) and you've got an incredible touch sensor. use this circuit to amplify the circuit before passing it into sound level detector.