I recently had the opportunity to build a lavalliere microphone. The goal is to have a lavalliere microphone drive a small audio amplifier with an appropriate signal level. Technically, the lavalliere ...

Here is an Electret Condenser Microphone – ECM preamplifier circuit based on ultra low noise BC650C transistors. Due to difficulty of finding BC650C, instead of them, as you can see in the schematic, ...