[Galaxy S II General] pspilot:
Jeez, I wanted to reply days ago, but I also wanted some more facts and clues. I even took my SGS2 apart to have seen 'its guts' at least :D ... not a hope to hardware hack anything in there, at least not without further knowledge about the design. Most components are shielded or on the wrong side, which means, you can hardly operate the thing while measuring or even modifying things. Also, it IS a design of LSIs, meaning not much left to discrete parts. The good thing about that is, alot more could be done by software. So ...

For me the 'mystery' still is: where's that proper headphone output gone that's burried basically in that chip? Looking at the datasheet of the 818 again, it shouldn't be that lousy. Also, Yamaha is no beginner, when it comes to audio equipment or electronics. I already stated, I have the feeling, the thing is not proper supplied. It can have more reasons, that different impendances of different headphones are making things better or worse, but there's hardly another explanation for an even weak output when connected to a 10kOhm Line-in. There's no swing with no supply, no matter what impedance :). Soooo ...

... perhaps there IS some 'analog control' and that's the power supply. I have no 100% proof yet, but it seems the SGS2 is supplied by a 'super-chip' from Maxim, the MAX8997. A press release or that news article seem to make quite clear, that the chip was developed for Samsung and their needs. Apart from other functions, that 'beast' is supplying not less than 7 switching regulators and, more important, 21! LDOs (low-dropout analog voltage regulators), which would be best suitable for the audio chip. The SGS2 for sure needs some independent supplies for all its functional block, radios and the CPU. But from 21 LDOs at least one or more would be left over for the audio. Unfortunately I could dig up a datasheet yet, it seems Maxim and Samsung are making a bit of a secret out of it, but I'd guess all these outputs of the LDO's are programmable and there you go with your analog control :). Yep, I know you meant something else. I'm still convinced that it would be worth to look into that 'supply matter'.

Jeez, I could write a novel here ... that SGS2 supply in general is another subject which is all but clean and clear. Only that much: definitely the SGS2 can consume more, than any AC-mode can supply. The intake is limited to 650mA, which is far too less for a loaded CPU, let alone charging in that time. The result are complaints, that i.e. while navigating in the car the device is discharging, even with an AC connection. Now my suspicion is, that Samsung can't really handle the full potential of a 1.2GHz Dual-core CPU in a 9mm case, heatwise :D. So they limited the intake and already the people start thinking, whether they can 'afford' a good running but demanding 'Navigon' or rather stick with weaker solutions, that consume much less. Anyway, under all these impressions, I have no doubt, that someone at Samsung said last minute, "safe power where ever you can, every mW counts" (reminds me of the movie "Apollo 13" ;)). Result was, that the Yamaha chip was also cut low. The data sheet of the 818 tells the rest. AVdd is always in the formula for the output power.

Well having all that said, there IS also a charge pump also on the Yamaha chip, which can be operated with different capacitors. If Samsung messed it up there, the power supply can't help. But hey, think positive :).

I can't say how bad that is, but I tend to find it not as bad as the missing power. Also, maybe the limited supply is responsible for that too? DACs are dynamic little 'things' and if the supply is not 'stiff' enough or in this case, doesn't have enough headroom, that's exactly what happens. But hey, these LSIs can or can't do anything - I have absolutely no intimite knowledge about that specific part. I wish I would.

100% agreed, even if I still wonder, what the 'AP clock' is :). But yep, a bad clock can indeed prevent any good digital audio (even worse on video). How do you come to the conclusion, that the master clock is not stable?

No need to be sorry, we're all here for fun - no sweat mate :D.

Now, if I'd be an adroid or linus coder, I'd look into these sources, which obviously deal with that supply chip :rolleyes:. Still, alot of facts are missing. To fiddle with these voltage settings, basically a schematic would be necessary. Then again, maybe the connection between the LDOs and the audio chip could be derived from the SGS2 sources? If that chip is used, the kernel has to take care of it, no? As I mentioned, I'm the guy with the soldering iron, without datasheets and schematics I'm helpless. But maybe I can at least point in the right direction. No need to say that messing with the supply chip can be extremly 'dangerous' for the hardware.

What's next? Well as I said, I could write novels here. Another 'subject' to look at would be the USB-audio out. Hows the quality there? Which original output is it anyway (some true audio output is only switched to the USB data lines)? The Yamaha HAS a line-out, but Samsung could also switch the headphone out. Can the flaws on the DAC also be observed there? My next 'project' will be an audio cable to my STAX headphone, which is still my best measurement gear, together with my ears, using that thing for over 10 years now :). Lots to do ...