This is a DIY mid-side condenser microphone with a built-in stereo decoding matrix and preamp. The microphone and preamp are powered by two 9v batteries, and the whole unit can be built on a Radioshack circuit board and housed in a modified Altoids tin. Awesome project for DIY field recording!

Notable Features:

• Uses two Panasonic WM-55A103 electret microphone capsules
• Switchable stereo or mid-side outputs
• Full microphone preamp with gain adjustment
• Adjustable stereo width
• Provides line-level output

Price: No products available.  Inexpensive bill of materials.
More info:

• Dave Latchaw’s website.