Hi !
I made a custom audio development board with an esp32 microcontroller and a WM8978 audio codec.
All inputs and outputs work great but now I want to go further by measuring S/R and THD.
The datasheet of the codec gives values for SNR and THD but depending of the quality of the PCB routing I think these values may be quite different.
The question I face is how to do the measurement for my board ?
If you look at datasheet P14 (https://www.mouser.com/datasheet/2/76/WM8978_v4.5-1141768.pdf) we have lots of routing possibilities.
If I generate a pure 1KHz sine wave to feed the input and put a probe at the output to measure the added noise/distorsion by the codec and the board, I have to test it for all inputs, all outputs, and all the possible routing scenario !? Because we can have lots of different signal path I think the noise may be different for each but what is the value I put when I describe the features of my board ? 🤔
It is the first time I have to measure audio quality so I'm a bit lost.
I made a custom audio development board with an esp32 microcontroller and a WM8978 audio codec.
All inputs and outputs work great but now I want to go further by measuring S/R and THD.
The datasheet of the codec gives values for SNR and THD but depending of the quality of the PCB routing I think these values may be quite different.
The question I face is how to do the measurement for my board ?
If you look at datasheet P14 (https://www.mouser.com/datasheet/2/76/WM8978_v4.5-1141768.pdf) we have lots of routing possibilities.
If I generate a pure 1KHz sine wave to feed the input and put a probe at the output to measure the added noise/distorsion by the codec and the board, I have to test it for all inputs, all outputs, and all the possible routing scenario !? Because we can have lots of different signal path I think the noise may be different for each but what is the value I put when I describe the features of my board ? 🤔
It is the first time I have to measure audio quality so I'm a bit lost.
You have to measure what you want to know... its that simple really - no obvious shortcuts with absolute promises....
But probably you would want to secure your addition to the spec - we will trust the spec... not many external components needed...
Basic in/out - incl lowest distortion paths...
Dig in, Mic, Line -> Speaker
Dig in, Mic, Line-> Phones
Dig in, Mic, Line-> Line out
Sa: 9
All the internal processing/routing have some impact... do a few on the one you will use....
Dig in, line in -> ADC filters -> Line out
Dig in, line in -> DAC filters -> Line out
Dig in, line in -> mix -> Line out
Sa: 3
That would be my take - good luck with the board!!
//
But probably you would want to secure your addition to the spec - we will trust the spec... not many external components needed...
Basic in/out - incl lowest distortion paths...
Dig in, Mic, Line -> Speaker
Dig in, Mic, Line-> Phones
Dig in, Mic, Line-> Line out
Sa: 9
All the internal processing/routing have some impact... do a few on the one you will use....
Dig in, line in -> ADC filters -> Line out
Dig in, line in -> DAC filters -> Line out
Dig in, line in -> mix -> Line out
Sa: 3
That would be my take - good luck with the board!!
//