NUCLEO-G031K8 ADC conversion for audio recording -- bit resolution and recording quality
Let's be practical and realistic but firstly this answer has got nothing to do with your preamplifier design - without a schematic it's impossible to say.
Anyway, CD quality is 16 bits stereo so, if you are happy with 16 bits then there is no great reason to go any higher in sample resolution. But let's think about a piece of music (say a solo classical guitar piece) on a CD. Let's say it starts quietly and builds to around half-full-scale resolution. &quot;Quiet&quot; might mean 20 dB lower than the middle-section of the piece of music so, if the middle-section is about half-full-scale resolution (16 bits) then it will have 15 bits resolution approximately.
Now the quiet section at the beginning might be 20 dB down (or one hundredth of the amplitude) and that means the resolution in those opening few bars is 6 bits lower in resolution i.e. it will have a signal that is equivalent to a 9 bit full-scale-signal.
And, when listening to a CD of a quiet intro on a piece like this, if you are still happy with the sound quality then you will be more than happy with 12 bits of resolution. If it's an electric guitar and has distortion as an FX then I doubt that you would tell the difference if less-than 8 bit resolution were used to encode the analogue signal.
Like I said: be practical and realistic.
What might kill your sound is if you are not sampling fast enough i.e. not sampling at least 40 k samples per second. If it's more like 20 kSps then you will begin to notice the difference and the top clean edges of the guitar sound will just start to be lost.
Another thing that might give annoyance is not using a proper anti-alias filter AND sampling at too low a rate. For audio, the general limit is 20 kHz and sampling is done at 44 kSps i.e. sampling is done fast enough to avoid problems of aliasing. Of course, with audio (and no ultrasonics picked up) you wouldn't need an anti-alias filter at 44 kSps but, if you were sampling at 20 kSps then you probably would because, anything between 10 kHz and 20 kHz might be &quot;bounced&quot; down into the digitized spectrum and sound awful.