MP3 player distortion measurement [shocking!]

[neutron7]

you have a low voltage battery. "power" op amps and D/A converters are not as good when they have low voltage single rail supply.
(not to mention apple etc is trying to squeeze every penny of profit, so they use cheap parts)

also the playback algorithm for a compact device (the thing that uncompresses the data) is also trying to save power, and also be as simple and cheap as possible. they are not all the same.

 

[Limhes]

Aah, I just found out it IS my sound card slightly clipping! I'm very sorry to put you all on the wrong track. Stupid thing is that I couldn't see it very clearly, since it started clipping just before maximum gain...

So, a good FFT would be:

An externally hosted image should be here but it was not working when we last tested it.

(With a full battery.)

Thanks for all your inspirational thoughts on this! I will never make this mistake again

 

[ezkcdude]

Re: Re: MP3 player distortion measurement [shocking!]

Aah, I just found out it IS my sound card slightly clipping! I'm very sorry to put you all on the wrong track. Stupid thing is that I couldn't see it very clearly, since it started clipping just before maximum gain...

So, a good FFT would be:


(With a full battery.)

Thanks for all your inspirational thoughts on this! I will never make this mistake again

I don't think you're alone in this. I've tried making measurements with my soundcard, but I just can't trust that I'm doing it correctly.

 

[hehe31]

i did a full rmaa test with my mp3 phone:

1st test is the mp3 file, because it don't want to read wav files :s (lame 192k)
2d test is my phone ( in line in of a fortissimoII, 16bit/44k)

Test mp3 sony
Frequency response (from 40 Hz to 15 kHz), dB: +0.61, -1.15 +0.58, -1.19
Noise level, dB (A): -97.5 -77.3
Dynamic range, dB (A): 96.9 73.8
THD, %: 0.0009 0.013
IMD + Noise, %: 0.048 0.072
Stereo crosstalk, dB: -98.1 -76.8

can you do the same tests?