Don't forget that the tests I reported are for PURE RESISTIVE LOADS. Real headphones have an impedance that will vary considerably with frequency (the "nominal" impedance of headphones I think is measured at 1 kHz). So maybe the impedance drops too low at some frequencies. Anyway, those "fuzzies" which show in the sine tones (on the scope) and sound like a "buzz" are well known in output driver stages and are circuit design issues. I'd be really surprised if any sort of firmware update could fix it and maintain the same outstanding characteristics that the S4 has. I updated the RMAA audio tests (for 32 ohm resistor loads) at the web page. My results are for open headphone output (what you'd get if you used a small external amp) and 32 ohm resistor loads are very similar to GSMArena's measurements ... probably the best audio performer of any current smartphone. So we really have to continue to leverage this to Samsung to get a proper response.
I wonder if different sets may be more 'lemon' than others.
I am trying to leverage this to Samsung, but it would help if everyone does their part to email Samsung about this. One person reporting this problem they'd probably ignore, but if hundreds or thousands come to them with the same issue it might do the trick.
Though I doubt Samsung will initiate a recall for this since realistically 99% of users will probably be satisfied with Samsung stock earphones. Just take a look at the 'screen smearing' thread, I think that is a much more minor issue than this but no one apart from a few of us seems to care about the amplifier issue which may be much more troubling.
By the way, I'm no sound engineer, but what exactly is the output driver stage? Is it part of the amplifier or the DAC? If it's the DAC then maybe we need to involve Qualcomm in this too. Is it connected to the motherboard or integrated to the 3.5mm jack? Take a look at the teardown to see how the S4's motherboard looks like: http://www.ifixit.com/Teardown/Samsu...ardown/13947/1
---------- Post added at 05:06 PM ---------- Previous post was at 05:03 PM ----------
Sorry that I have to post again, but I tested it again and it is interesting... it is not the volume, it is the frequency.
Two different songs, one is crackling at ca 70% volume other song, not crackling at 100 percent although the bass is not "unheavy", too...
All the best
Gesendet von meinem GT-I9505 mit Tapatalk 2
BTW, on your rooted phone are you using a custom kernel or still the default kernel? Are you sure it doesn't happen on the stock ROM for you? Maybe you would want to try again! Or is it two different S4s you are talking about?