Most consumer-grade cameras these days come with adequate microphones built in. However, as with all hardware made down to a price point, there’s room for improvement. [M. Ploegmakers] decided to whip up a better microphone setup for his Sony A6300, with the Dumbbell Mic as the result.
The microphone is based around an electret condensor element, which provides good performance at a remarkably low price. This is then integrated with a preamp circuit to bring the audio up to the appropriate level for the camera to record along with the video. Switches on board set the gain level, as well as changing the mic to operate with or without phantom power, where available. The electronics is wrapped up in a 3D-printed enclosure, designed to mount on top of the camera for use out in the field.
It took some experimentation, but now [M. Ploegmakers] has a custom mic rig that records straight into the camera, avoiding the need to splice audio and video back together in post. If your camera lacks an audio input, you might have to do a little more work to hack one in, though!