However I have a few questions which seem noise-related:
1.) What is the purpose of the opamp on the 2.5V line (marked blue)?
And why are there two of them in parallel on your original schematic (I guess to average out their noise, but I'm talking out of my a**)?
2.) Why do capacitors in pink have different values and why do they have the values they have?
3.) Why are there so many capacitors between 2.5V line and the ground? And why 100nF? (marked green)
4.) The capacitors and resistors marked in yellow are ~8K low pass filters you were suggesting in post #3?
5.) Why are there two Gain x5 opamps in each channel? Why is there not only one with Gain x25?
Based on my questions so far, can you (or anyone else) recommend some book/blog/resource that would help me better understand concepts in audio circuits?
I will try to answer some of those questions, in order so as to possibly make sense.
Well, I would, except that they have ALREADY BEEN ANSWERED QUITE WELL IN POST #20
I will make an additional point relative to why have two stages when one stage can easily provide that much gain. The portion of the answer not really explained in detail is the "gain bandwidth product."
In addition to noise considerations, almost every amplifier is limited by that product. The result is that as the gain is increased the frequency response is reduced. Along with the frequency response reduction there is an increase in non-linear distortion. How much?? Not very much but distortion in a stage multiplies the distortion in other stages. Again, possibly not much, but if the goal is none, then some, or "just a little bit" may be too much.
Hopefully this explanation is useful and not excessively confusing.
To a self-tought beginner comming to analog circuits from arduino-level digital basics, it's easy to form a naive understanding of what components and circuits do, so every bit of information helps.
Your explanation makes sense. Thank you.
Facebook
Google
GitHub
Linkedin
