>>12353>stationary PC.So a desktop box ?
Assuming the user hasn't plugged in a mic or a low impedance headphone, what are you using as microphone ?
Those cheapy speaker boxes that people usually use, have classD amps, while, efficient, low cost with reasonable audio fidelity, they have a terribly high noise-floor. I doubt that you can get usable audio capture from that.
A class-D amplifier or switching amplifier is an electronic amplifier in which the amplifying devices (usually MOSFETs) operate as electronic switches, and not as linear gain devices as in other amplifiers. They operate by rapidly switching back and forth between the supply rails, using pulse-width modulation and pulse-density modulation to produce a pulse train output.That leaves the motherboard-beeper, which usually is just a piezo connected to a 5v IO pin that goes high-low-high-low square-wave at 500Hz. Can you get audio capture from that ?