Thursday, June 20, 2013

Making Microphones, or: Toys!

I admit it, I'm a broken electronics hoarder.
This can be a curse when I'm looking for a place to put old whatchamacallits I don't have the heart to throw away, thinking "I'll find a use for this someday," or "No, waaant!," but it can be a real blessing when a big idea comes along and I can find my soldering iron.

The Hoard
A few days ago one of those moments occurred: I had wire, a pile of piezo transducers I'd acquired from ebay, a little bit of money, and my soldering iron was waving at me.

Here's what was borne of those ingredients:
First, a contact mic.
This one was the simplest as it only required the piezo, a 1/8 mono plug, wire, shrink tube, some Plasti-Dip and patience.
1. Solder the wire to the piezo.
2. Slip the shrink tube and plug casing on.
3. Solder the plug to the other end.
4. Shrinky-time :)
5. Thread on the plug casing and dip the mic end into the Plasti-Dip
6. Wait 4 hours and try to find SOMETHING to do.

Oh look, goop.

The next day I had a thought.
"It smells funny in here."
 No, that's the wrong thought...

Yeah, that's the one.
So I set off on a quick internet search, looked at different versions that do-it-yourselfers have come up with, and descended into the basement to look for usable junk. Eventually I found some prescription bottles and realized the caps would be just the ticket.

That's the childproof pushy-downy thing.
After a bit of razorblade alteration, the piezo fit into the center ring of the cap like a cradle. I drilled a hole for the wires and was off and running.

Piezo, all snuggled up.
Stringing the wires through.
The next step was to make a hot gluey mess and squish the plastic childproof springy thing back under the tabs that originally kept it in place.

Then I stared at it for a while, hoping I didn't heat the piezo to destruction.

This thing needed to be capped (hah, whoops) off, so I grabbed another pill bottle cap, a hacksaw from the garage, and a vice. Sawing it up created a tiny frisbee that was tempting me to play with it, but I restrained myself because there was work to do.

Quick, catch!
After some careful razor work I was left with a pile of stuff.
Hey it fit right on there. Fun!
Add hot glue, squish.
Note added 6/23: I wish I'd thought to add something heavy in the second round of hot glue. A thick washer maybe. The thing floats a bit.

I went through the same steps as the contact mic to connect it to a mono plug, then dipped her in some sludge.

I had a really hard time not eating this.
It looks sloppy above, but Plasti-Dip shrinks as it dries.

Once again, wait 4 hours and find something to do...

OOH! Inductive microphone!

Inductive mics are just coated wire coiled around iron--or high iron content if none is available--rods, so that's easy, right? Not in my case, but thankfully I had a magnet and a drawer full of bolts in the garage. As for the bolt, my father is a welder/fabricator, so it was easy to saw the threads off. I also have bunches of inductors and transformers scalped from broken things, so the wire was available.
If you like spending as little time as possible, buy the wire. I didn't. Instead I unwound an iron torroid inductor, because when testing it as it stood I couldn't pick up much in the way of electronic noise. Does the circular shape prevent it? It's a mystery.

Center: iron torroid inductor with far too many turns of wire.
Here's what a mess of wire, some hot glue, and my bolt that a magnet found especially attractive became.

Three cups of coffee and a hot glue gun created this. Induce! Er, induct!

So after a couple days spent in the basement huffing solder fumes and playing with what normal people would call garbage, I now have 3 new microphones.
Three microphones lounge atop a gas grill on an idle afternoon.

Play with trash! Make stuff!


  1. When do we get to hear these bad boys? :)

    1. Very soon. Tomorrow perhaps? But tonight I'm off to drown my blech birthday sorrows. To the beer!


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