Making Microphones Part 2 - Some Samples

So I've been using the microphones the last couple days and I'm pretty happy with them, barring some minor issues.
I wish I'd thought of the fact that the hydrophone needs to sink. There ought to be a washer or something inside the second layer of hot glue.
Because I'm not using a preamp the gain needs to be cranked when plugged into either the external mic or line in inputs, so there's some white noise. Guess that's something else I'll be building soon...

Here's some stuff!

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...

"Hydrophone."

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.

*Splort*

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.

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.

See?

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!