/diy/ - Do It Yourself

Latest WIP: a fully differential audio amplifier
Shitty old car has shitty old head unit/amplifier that is dying. Instead of buying some walmart piece of shit with 5000 LEDs in it I thought I'd have a go at making my own and using the original face/knobs.
I don't want to fuck around with a class D amp and I don't want to fuck around with switchmode power supplies; getting any amount of power out of the meager ~13.8 V the alternator spits out demands running the speaker between two bridged amps, which still only maxes out around 16-20 W per speaker, but that's still plenty loud enough for me and my tiny car. The normal way to bridge amps is to just build two of them and use some op amps to invert the signal going into one and wire the speaker between the two outputs, but then there's the possibility of DC offset and burning up the speaker if the two amps aren't identical and the op amps have anything but zero dc offset. So, the idea is to forgo coupling the speakers with huge expensive capacitors and just build one amp with differential output so that the feedback loop keeps DC at zero between the two outputs. Differential output also has a few nice quirks: The load is put inside the global feedback loop, so even-order harmonic distortion is reduced significantly (according to a TI app note on their differential op amps). I'm using retarded amounts of medium-power transistors on the outputs in parallel because I have literally got bags of them laying around. They should do fine since I'm only working with 14V.