Headphone Amplifier & Mic Preamp This project is a simple headphone amplifier and microphone preamp. It supports a variety of TRS and TRRS audio connector standards. It also includes mute, variable gain and activity monitoring. This project has been successfully implemented and tested, the prototype works with only a couple of small fixes. Most of the bugs found have since been corrected in the trunk version of the project (in case I or anyone else decides to make more of these). The only other issue of note, is that there was still more headphone to mic couple through than desired... The mic-preamp stage may need a bit of work to improve this! TODO: V switch - This should disconnect the power entirely, rather than just control the LDO enable (otherwise there can be significant leakage current while off, which is an issue for battery power). Mute Light - shouldn't turn on when power is off... Hysterisis issue - monitor is not sensitive enough Space out connectors and knobs - it's a little tight Fix Fuse footprint - fuse footprint was incorrect Fix C22 Footprint - this needs to be slightly bigger Check Ferrite Footprint - Bigger