If the car radio is new, maybe it has an all-digital Class-D switching audio amplifier. They are so efficient that a small surface-mount package can provide 4 bridged amps without requiring a heatsink.
I don't want to touch those amplifier ICs because they have 56 tiny legs and their "power-pad" bottom is also soldered to the PCB. Try doing that by hand!
My car's factory radio/CD player must have 4 bridged amps because both wires for each speaker carry the signal. After replacing the crappy high-impedance tiny-magnet factory-installed speakers with half-decent 4 ohm big-magnet ones, I get more than enough power/volume.
Yeah, its volume control must be digital too, because you can turn it around and around. It must provide "up-volume" or "down-volume"
pulses using an optical or hall-effect sensor then stores the setting in memory.
