dawsonjon
AUDIO CODEC
Hello Mr. Jon, I have a request to make. The PICORX project is very good, and I don't know how to contribute. I assembled it and loved it, however, there's a lot of noise, and it's not even background noise. So I'm asking, wouldn't it be more interesting to add an audio codec to the output so we can have a cleaner sound? A more popular and easy-to-obtain codec?
Hi,
Yes its a great idea! Something I would like to explore in future more sophisticated versions of the design. You can even get amplifiers with i2S inputs which might work quite well in this type of application. An audio DAC certainly outperforms a PWM DAC by a considerable margin. An typical audio DAC has more than 25kHz of bandwidth and an SNR of nearly 100dB. The PWM DAC probably gets an SNR of maybe 50dB and about 3kHz bandwidth (the way its configured in this design, you can trade SNR for bandwidth by changing parameters). While PWM audio is nowhere near as good as a proper audio DAC, it is still quite a lot better than a strong AM station! In this particular application you wouldn't be taking full advantage of the DACs improved audio quality. The USB audio is just as good as you would get with an audio DAC if you want to get an idea what it would sound like. Another idea that would give a massive performance improvement would be to use an audio DAC in place of the Pico's built in ADC. This would give a huge improvement to the receiver's sensitivity and dynamic range and would probably even reduce the processing load. I have used the PCM1802 in previous projects, its easy to obtain (in module form or as a bare IC) and performed very well. Its all stuff I would like to explore in the future, but it probably deserves a project in its own right.
Cheers Jon
