I have some 1/4 mono cable and I'm wondering if pulling off the end and taping the open cables and taping them to a square of sheet metal would give me a sort of contact mic? How delusional am I? Would it work?
the short answer is no. the longer answer is that vibrating (striking) any kind of metal, including just the wires themselves, will generate a signal. you can get a few micro-volts with a sharp hit with a chopstick, and some nano-volts from speaking into it. so, if you have an amp that can amplify that without too much noise, you're good to go.
The way that a contact mic actually works is to apply pressure to a crystal. I fail to see how vibrating a sheet of metal would actually produce voltage, even in the nano volt range. There just isn't a difference of potential there. Or do you think that having different areas of the sheet metal will somehow produce an effect because of its proximity in the earth's gravitational feild? Please explain.
> I fail to see how vibrating a sheet of metal would actually produce voltage
sure, it's not obvious, but i've seen it in action when testing some very high gain amps, and it has a name, and a wikipedia page, only i dont remember what it's called.
I taught an audio lab during grad school. One of the labs was to make a capacitive mic using a metal plate and a few sheets of mylar. It didn't work very well.
I don't think you're gonna get much out of a plate by itself. Static zaps maybe.
Try mixing different materials if you want the vibrations to generate voltage.
Also I highly recommend using an amplifier, you can pick up a pack of 5 3w+3w amps off eBay for aud 2.50 last I checked.
Sort of true but irrelevant. Most metals are polycrystalline. You can only make a pressure sensitive crystal mic out of a "single" crystal or "perfect" crystal. You never made it through 8th grade science, eh?
I like the idea of making a capacitive mic out of a metal sheet though. Just fix one large metal plate in place, cover it with plastic wrap, connect one of your wires to it, then connect your other wire to a separate metal plate that is close to the first one, solder your second wire to it, then strike it with a hammer.
Of course, you would need a preamp that is *extremely* low noise with a gain or, maybe, 100,000X.