He is an electronic det can that I made for tuning.
item needed:
- 12v amp board https://www.aliexpress.com/item/1005...Cquery_from%3A
- knock sensor (any 2 pins will work) https://www.aliexpress.us/item/10050...apt=4itemAdapt
- M10X1.25 stud to M8 https://www.miataturbo.net/miata-par...sensor-109021/
or (modified) https://www.aliexpress.com/item/1005...16ce1802g1UcOd
- The 3D printed case https://www.thingiverse.com/thing:6516599

First, you need to modify the aliexpress stud (or buy a good one)
I used a drill and angle grinder, you only need about 3 threads on the stud to be ok.




Install the knock sensor in the middle of the block, and pass the wire to the cabin



Install wires on the amp for the 12v and the audio output (the left and right channels are together)




Close the case with #6X1/2'' wood screws





Best use a 12v battery for power to isolate from all electrical noise.
Install a 3.5 audio jack on the knock sensor wire and plug it into the input of the amp.
Connect a pair of headphones on the output and a 12v battery and adjust the volume.



Here I have a volt meter in series to keep an eye on the voltage to not kill the battery.