bootlegMIC Assembly

Note: You can click on the pictures for higher resolution images.

0. Tools

To assembly your bootlegMIC, you will need a pair of cutters, needle nose pliers, soldering iron, solder, and something to hold your mic in place with. A set of “helping hands”, or a mini-vise are great for this. You will also a need a sharp X-ACTO blade or razor blade. Good lighting and a magnifying glass can also come in handy.

1. Check your parts

You should have received one each of: 470ohm resistor, 2.2k resistor, 22uF capacitor, electret microphone, and 1/8″ jack. If anything seems amiss, notify Open Music Labs immediately.

2. Prepare the microphone

The electret microphone needs to be modified, to change its amplifier configuration. To learn more about this, check out the wiki page. To do this, first find the Ground Pad. This is the one with the leads that go the case.

You will need to cut the Ground Pad in half, so the side with the pin is completely disconnected from the side with ground traces. To do this, use a sharp razor blade, and cut 2 slices, very close together, between the pads.

Keep digging those 2 cuts deeper with the razor blade, and you will eventually clear out a small channel between the 2 pads. You can run a small screwdriver back and forth in the channel to get rid of any copper or solder that might be left there. Just to be sure that you completely seperated the 2 pads, you can use a multimeter to measure the resistance between them, which should read open circuit.

The 3 pads on the bottom will be called Ground Pad, Source Pad, and Drain Pad. Again, the wiki has more information on why this is the case. Now, use a pair of diagonal cutters to remove the pin that is attached to the Source Pad.

And your microphone is now ready to be attached to the rest of the parts.

3. Attach the 2.2k resistor

First, locate the 2.2k resistor. It is the one with 3 red bands on it. Next, bend it in half, and cut the leads as shown below.

The 2.2k resistor gets attached to the microphone as shown below. The long lead goes to the Ground Pad, and the short lead goes to the Source Pad. It helps to pre-tin (put a bit of solder on) the ends of the resistor before soldering them to the microphone. It’s important to not spend too much time heating up the microphone. Get the pad hot enough for the solder on it to melt, attach the resistor lead, and let it cool. Then go on to do the second lead in the same way. The electret microphone uses a very thin film of plastic as its sensing element, and this can be damaged from too much heat.

4. Prepare the 1/8″ jack

The 1/8″ jack used for the bootlegMIC has 4 conducting rings on it, which is standard for most cellphones. If you want to use the bootlegMIC with a computer or other recording device, you will need a 3 or 2 pin jack. The assembly is the same in either case, as you only use 2 of the conductors anyways. First, unscrew and remove the plastic casing.

Next, cut the Signal Tab of the jack, directly above the small hole.

5. Solder the mic to the jack

The Ground Pad of the microphone gets connected to the Ground Tab via the long leg of the 2.2k resistor. To attach the two parts, first pre-tin both the 2.2k resistor (right at the bend) and the Ground Tab. Then hold them together, and heat them until the solder melts and they join. This is made easier by using a mini-vise.

Next, solder the Drain Pad of the microphone to the Signal Tab of the jack.

6. Attach the 22uF capacitor

First, locate the Negative Pin of the 22uF capacitor. This is the one next to the stripe with the (-) symbol on it.

Then, cut the leads of the 22uF cap short, as shown below.

Next, bend up the Negative Pin, and solder it to the Ground Tab on the jack.

7. Attach the 470ohm resistor

The 470ohm resistor has yellow, purple, and brown bands (in that order). This resistor goes between the 22uF capacitor and the Drain Pad on the microphone. Again, pre-tin the parts, and solder one end of the 470ohm resistor to the free lead on the 22uF capacitor. If you want more or less gain from your microphone, swap out this resistor with a larger or smaller value. See the wiki for more details.

Then, solder the other end of the 470ohm resistor to the Drain Pad on the microphone.

Finally, trim the leads to tidy up the package.

8. You are finished!

If you want to fill in the voids with hot-glue or epoxy, that would make a more robust package, but it should work pretty well as is. Now go out and record loud stuff!