Bit Crush
The lo-fi knobs, measured. Eight bits puts the noise floor 48.9 dB down, a tenth off the textbook figure, and turns a note at -40 dB into 27% distortion. Four bits gives 25 dB and that quiet note comes out as nothing at all. Dither brings it back as a tone in hiss for 4.9 dB of noise, and holding samples at 6 kHz grows a 1 kHz tone two images at 5 and 7 kHz, -14 and -17 dB, where the sinc says they should be.