I just finished the first audio tests today, comparing the audio output of a semi-professional USB Interface (FocusRite Scarlett), a Pandora and the TWL6040 on the PandaBoard (which is the same we plan to use for the Pyra).
The test I wanted to do today was testing the audio output of the DAC, not the quality of the amplifier (which will be tested with a different test).
I'vee created an Audio file (48kHz, Uncompressed, 32bit, Mono) has been played back with a PC (FocusRite), a Pandora and a PandaBoard (also uses the TWL6040).
Each device was then being recorded (with another FocusRite Scarlett) and analyzed with Adobe Soundbooth (just a quick analysis).
The result was quite surprising: I expected the TWL6040 to be the worst one, but actually, the TWL6040 DAC seems to be a bit better than Pandoras one - except when it comes to noise: Then the Pandora wins of all devices.
I guess the bad audio quality with these days devices is the amplifier, not the DAC. But that will be tested as well. Well, and it seems DACs have become better within the last few years.
You can download the full report with graphics from here: http://evildragon.openpandora.org/AudioTest.pdf
And here (http://evildragon.openpandora.org/AudioTest.zip) is a set including the following: 1. Original WAV-File (that was played back) 2. Each recording from every device (compare the playback quality yourself) 3. Three small WAVs where the audio device is switched while audio is playing (see AudioTest-Report for more information).
Questions? Requests?
Discuss about that post on the webboards: http://boards.openpandora.org/topic/17161-first-round-of-audio-tests-done/
Follow me on twitter for short news inbetween: https://twitter.com/EvilDragon1717