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I politely disagree here.
The main CPU of smartphones is usually more power hungry than dedicated audio chips because it has multiple cores and is designed to manage a huge variety of tasks.
A dedicated audio DAC can allow battery saving. The amp part is another story. You need a lot of power mainly if you want to power large headphones, it is not a prerequisite for most IEMs.
There are half a dozen examples of smartphones where the dedicated audio part is there to save power on top of allowing lossless format decoding.
And the same is true for DAPs not using an Android-based system, they're usually more economical on power because they don't extreme PU power and high-res screen (Cowon DAPs were great examples before Plenue 1/M/S).
Android has been the bane of autonomy so far, because the high res screen and versatility expected from smartphones requires powerful CPUs. The audio part is not responsible for autonomy decrease. Having the main CPU handle audio is for saving cost, nothing else.
Ok, I can agree with some of that.
Like phones need powerful cpus, but these are developed in a specific way to aggressively save power. I mean the whole SoC is a bunch of circuits, including the cpu itself and all of these things in there are actively switched on and off all the time, because there is one very specific goal, not empty the battery too fast.
Sure, the screen backlight can't be switched off (assuming non oled screens here) and so many pixels have to be pushed around all the time for the thing to look cool. Can't get around that because we have to sell them phones.
My non educated guess is that inside the SoC the internal sound circuit is operated on-demand most of the time if not all the time, that is, turn it on just in time to play something then quickly turn it off, just like all other circuits in the SoC including cpu cores, modems, GPS circuitry etc.
But you can't turn off an external circuit like dedicated dac / amp in the aggressive way the SoC turns on and off what is inside the SoC itself. It is not a simple thing to implement, this technology was developed with this kind of energy saving in mind from the outset and this is one of the reasons Intel's cpus can't do it, cause you can't retrofit this in anything already designed differently.
Anyway, this is my understanding of the circuitry in a modern phone. If it wasn't for that, it beats me why anyone configures a hifi phone where the user switches that circuit on only when he needs it. I mean, why is it not always on? Would it bother users if it was always on, playing anything that needs sound output? All that would be required was a kernel instruction that would re-direct any call for audio output to the external dac / amp, end of story. So why don't they do it? Google doesn't allow it? Don't think so.
My only answer is that it costs way too much in power demand to have that circuit always on, I bet it can't even sleep proper at all, and most of the time it wouldn't be playing anything so why have it on, it would only kill battery life and make the whole phone look bad in reviews and such.
Just my 2c.
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