Stereo Microphone

It has come time for me to update my home recording studio to continue recording my own brand of intergalactic low-fi, disco, funk, folk rock. Rather than spend big bucks on a stereo mic setup that won't offer me the low quality sound that I am accustomed to, I have decided to build my own for next to nothing almost entirely out of found parts. Now I can get awesome panning effects that can easily be mimicked in software, but never truly replicated.

For those that don't know what a stereo mic is, it is basically using two microphones to record to both the left and right audio channels of a stereo music track to give that "3D" effect.

You will need:

- A flexible lamp arm
- 24" x 6" sheet of 1/8" acrylic
- 12" x 12" sheet of 1/8" milky white acrylic
- A laser cutter (or handsaw)
- A heat gun
- An oven mitt
- Table clamps
- An IKEA clock frame
- Two metal washers
- Two 1" (or larger) rubber grommets
- Two dynamic microphones
- A dozen LEDs
- Two BC546 transistor
- Two 100uF capacitors
- Two 2.2K resistors
- Two 47K resistors
- A 220 ohm resistor
- A 5V power transformer (give or take 1 volt)
- Red and black solid wire
- A panel mount stereo jack
- An SPST pull cord switch
- A power drill (with assorted bits)
- Assorted hand tools

Cut your acrylic using the following templates below.

One is for the bracket that holds the microphones, another other is a cover to make the base of the mic look all pretty-like and the last is a perf. board for building the circuit (print 2 or 3 of these using your extra scrap material after making the other cuts).

I laser cut them with a 75W laser with the following settings:
Speed: 12
Power: 100
Frequency: 5000

If you don't have a laser cutter, print out the template and tape or draw them onto your material. Proceed to cut them out with the tools you have.

Bolt your microphone bracket centered upon the flexible lamp arm.

Clamp the flexible rod to the table and slowly heat it with the heat gun until the sides start to flop.

The acrylic should be getting rather hot, so I recommend using an oven mitt.

Bend the acrylic into a U-shape until you are happy with the results. Let it cool to harden.

If you are unhappy with the final results, just re-heat it and try again.

Carefully insert your rubber grommets into the holes on each side of the bracket.

Gently push them into place. Don't be too forceful, as you might snap the plastic.

Place your microphones gently through the holes, angled towards each other, until they are held firmly in place.

Now we need to drill holes around the inner bottom of your clock for your LEDs.

I first lined this part with tape and marked it because I didn't want to put any extra markings on the case itself (in case I made a mistake).

I then drilled the holes.

Insert your LEDs into the holes, pointed towards the inside of the case. Wire all of the longer power pins together and all of the shorter ground pins together.

When you are done, solder one end of your 220 ohm resistor to any of the ground pins.

Drill appropriate sized holes for your audio jack and pull cord switch and then insert them into the case.

Also, cut the end off of your 5V power transformer and pass that into the center of the case. This may require drilling an extra hole on the surface the LEDs are in (so the wire can be passed through). Once pass through, tie a simple overhand knot, so that it is held in place.

Build a circuit (as shown below) into your laser cut perf board.

Once done, build another.

Following the schematic, wire and glue the two boards in the part of the clock frame where the clock mechanism used to be.

You should be able to wire up everything at this point, but the microphones themselves.

Remember not to cover the center hole, because you will be passing the rod through it in the next step.

Drill a hole in the center of the plastic clock face cover and insert backwards (face down) into the clock frame.

Slide the acrylic cover you made in stop two onto the rod.

Clamp the rod the clock base using washers and nuts

There are two wire coming out of the microphone.

One is a ground wire and should be wired to ground. The other is the audio signal wire which should be wired to audio in on the preamp.

Wire a microphone to each of the pre amps.

Now you are ready to rock.

Have fun.

Some minor aesthetic improvements you may consider are:
1. Adding a weight to the inside of the base to make it a little less top-heavy.
2. Adding a felt circle to the bottom.