I've added the Push To Talk / mute module! The switch selects mute / always talk / external pushbutton to talk mode. LED lights when you're "on air". Mute mode mutes the yellow trace (output audio) but not the pink monitor level trace, and there's also an open collector external push-to-talk output to drive things like radio transceivers.
Making progress on my headset interface. The PCB underneath is the motherboard and power supply, then I have the microphone preamp and tone control boards plugged into a breadboard as the female sockets for the motherboard haven't arrived yet. Scope shows two outputs from the tone board - line level in yellow and doubled amplitude for the level meter board in pink. Next up: finishing the mute/push-to-talk control board and starting on the level meter, which should be fun!
#electronics #makerI made some steps to make it easier to get up this slope
#maykeSo, the standard Baxandall tone control circuit - the "Bass" and "Treble" knobs on every hifi - turns out to do next to nothing to human voice in my microphone pre-amp, probably because voice is in the 300-3000Hz range while the tone control is built for a much broader range found in music, which means I'm gonna need to design my own circuit rather than going off-the-shelf. Not a problem, just means I can't get to the much more fun VU meter stage yet!
Two stages of low noise transistor class-A amplification, then once it's up to levels where noise isn't a problem, an op-amp for final gain tweaking and a nice low impedance output drive. Slightly overkill, but I wanted to put learning to practice, so made it a belt-and-braces design.
What have I been
#mayke-ing lately? The white box on the left is a breakout from Baofeng/Kenwood headsets to separate standard ear/mic/push-to-talk leads; the PCB it's plugged into on the right is a microphone pre-amp that powers a microphone and brings the signal up to line levels! And both actually work!
Me also on the phone with my pals
Me on the phone with my pals
Completed my Baofeng/Kenwood radio headset to separate headphone/microphone/push to talk adapter. Combined with a separates->android TRRS combiner, I can place phonecalls through my funky radio headsets and fist mics!
Thinking about designing a curve tracer, based on the octopus design but driven from a DC supply and with better output isolation
