Homemade Plate Reverb
The first step is to attach a socket to your piezo disc – I used a 3.5mm mono socket (female), although you can substitute this for whatever connection you’ll be using most. Simply solder the positive (red) wire from the piezo disc to the tip connection on the socket and the ground (black) wire to the sleeve connection. I made a mono reverb so used just the one piezo disc, although you can add another to make it stereo.
While leaving the glue to dry I made up a timber frame to suspend the sheet metal in.
Once the frame was made and the glue dried I set about suspending the sheet in the frame. I drilled a small hole in each corner of the sheet and threaded through some wire (I initially used solidcore hook up wire, but this is far too weak. I am currently experimenting with tensioning bolts and springs to allow for ‘calibration’ of the reverb). I used some heatshrink tubing to stop the wire snapping against the sharp edges from my freshly drilled holes. The wire was then screwed into the inner edge of the frame.
Although this reverb can work well just picking up ambient sound (when the output is amplified) it is nice to be able to feed a signal directly to it. So I added a small piece of MDF to the back and cut a hole in it to allow for a speaker to be placed next to the plate (I purposefully didn’t fix the speaker in place to allow it’s distance from the plate to be adjusted according to taste.
Ideally I plan to build a battery powered amplifier circuit for this speaker, but at the moment it is still attached to the computer speaker housing and amp that it originally came from. I have simply extended the wires connecting the speaker to the amp.
The output from the piezo disc is pretty low so it will need to be amplified. For this reverb I built a preamp circuit and housed it in an old tobacco tin (Post on how to make this coming soon).
This unit needs tweeking to fine tune the resultant audio, by tensioning the plate more, adding a mechanism to dampen the vibrations or many other little amendments that will be added to this post once researched and implemented.