What is this BS coming from my phone?

[bachatero]

I was trying out some DAC performance tests when I connected up my Android phone's headphone jack and found this weird FFT spectrum.

At -80dB below the peak, the 2kHz harmonic doesn't look too bad. But what is that huge spike at 250Hz? To rule out a bad DAC, I connected up an external adapter and the result was the same. DACs usually don't exhibit this behavior, so I'm suspecting it's some BS that Android is doing to the output, and it might actually be audible. Has anybody else found something like this?

 

[Sokel]

I was trying out some DAC performance tests when I connected up my Android phone's headphone jack and found this weird FFT spectrum.
View attachment 406909
At -80dB below the peak, the 2kHz harmonic doesn't look too bad. But what is that huge spike at 250Hz? To rule out a bad DAC, I connected up an external adapter and the result was the same. DACs usually don't exhibit this behavior, so I'm suspecting it's some BS that Android is doing to the output, and it might actually be audible. Has anybody else found something like this?

That one looks worst than a 40 yo preamp when caps gone bad and mains noise has a party
Strange.

Edit:What's the test signal used?

 

[Blumlein 88]

I don't know about your particular case, but yes Android phones can be weird in what they output sometimes. At least a few years ago they were. I'd think they have improved. But I've not tested any in quite some time. Might as well tell us what phone it is.

I put up files recorded from several DACs on another forum a decade or so back. I asked people to rate them by preference without saying what was what. One was my phone DAC which has some odd response like a roll-off already down by 15 khz and near nothing above that. Similar at the low end. It had noise that you might hear if you were sharp eared. To my surprise almost no one noticed. One person who did notice was well known in some audio circles. Only he praised that DAC from the phone as being the only one that sounded good out of the bunch.

 

[Jimbob54]

Try a free trial of uapp or the hiby player app. Both can avoid the android stack and any resampling . I'd bet there's some funky DSP somewhere in the phones settings

 

[bachatero]

That one looks worst than a 40 yo preamp when caps gone bad and mains noise has a party
Strange.

Edit:What's the test signal used?

I used a simple 1kHz sine test tone, set to the right channel only since it's plugged into a balanced input. Also, the phone itself is the "Moto G Power (2020)"