ADC/DACs are still relevant, but I'd say digital is eating the world! Your two analog examples are actually great use-cases for all digital signal chains.
For image capture, you get much better dynamic range and lower noise if you capture pixels as single bits integrated over time. So, for example, you charge up a pixel array and then check all the pixels periodically to see which have flipped. Brightly illuminated pixels flip quickly. You get to pick how long you want to wait. At the limit, you can have pixels that are single photon detectors/counters (these actually exist today, just too low res for cameras... for now). Light itself is inherently digital, better to process it in its native domain! :)
The most efficient and lowest distortion way to drive a speaker is similarly digital. You basically send a series of bits at a much, much higher frequency than the highest audio frequency thought the entire amp chain and then let the inductance of the speaker coil integrate all the bits into the movement of the cone. Because the amps are driven rail to rail with very well defined edge transitions, they spend as little time as possible in their noisy and power hungry non-linear region. Here is also no noise to get amplified- you just get out much stronger versions of the exact same bits you put in.
Hal Chamberlin mentions that a 24(?) bit DAC built from discrete components would lose its linearity just from the effect of a lit cigarette held a few inches from the resistors. (That’s my recollection, anyway, I read his book long ago)
ADC/DACs are still relevant, but I'd say digital is eating the world! Your two analog examples are actually great use-cases for all digital signal chains.
For image capture, you get much better dynamic range and lower noise if you capture pixels as single bits integrated over time. So, for example, you charge up a pixel array and then check all the pixels periodically to see which have flipped. Brightly illuminated pixels flip quickly. You get to pick how long you want to wait. At the limit, you can have pixels that are single photon detectors/counters (these actually exist today, just too low res for cameras... for now). Light itself is inherently digital, better to process it in its native domain! :)
The most efficient and lowest distortion way to drive a speaker is similarly digital. You basically send a series of bits at a much, much higher frequency than the highest audio frequency thought the entire amp chain and then let the inductance of the speaker coil integrate all the bits into the movement of the cone. Because the amps are driven rail to rail with very well defined edge transitions, they spend as little time as possible in their noisy and power hungry non-linear region. Here is also no noise to get amplified- you just get out much stronger versions of the exact same bits you put in.
Hal Chamberlin mentions that a 24(?) bit DAC built from discrete components would lose its linearity just from the effect of a lit cigarette held a few inches from the resistors. (That’s my recollection, anyway, I read his book long ago)