Earlier than the invention of microelectromechanical system (MEMS) microphones, nearly all microphones in cell telephones and different electronics had been a kind of condenser microphone referred to as the electret microphone. The truth that this kind of microphone is reasonable and simple sufficient to position into shopper electronics doesn’t imply they’re all low high quality, although. Electret microphones can have quite a few qualities that make them fascinating to be used recording speech or music, so when you’ve got a struggling artist buddy like [fvfilippetti] has who wants an affordable strategy to carry one to life, check out this electret microphone pre-amp.
The primary purpose of the mission is to reinforce the efficiency of those microphones particularly in excessive sound strain stage (SPL) eventualities. In these conditions problems with saturation and distortion typically happen. The preampl design incorporates suggestions loops and an AD797 opamp to cut back distortion, improve acquire, and keep low noise ranges. It additionally contains an output voltage limiter utilizing diodes to guard in opposition to enter overload and might modify acquire. The circuit’s topology is designed to attenuate distortion, notably in these excessive SPL conditions.
Actual-world testing of the preamp confirms its skill to deal with excessive SPL and ship low distortion, making it a cheap answer for enhancing the efficiency of electret microphones like these. If you wish to go even deeper into the weeds of designing and constructing electret microphones and their supporting circuitry, check out this construct which discusses another design issues for most of these units.
