I am working on a color organ and want to use a design similar to this. I understand the gist of the schematic, but I have a few questions about it and how it works.
First: I understand that it is trying to tell me how to hook up my input audio signal, but I don't understand what it is telling me.
Second: This is describing a potentiometer connection, right? If so, do you know why having a potentiometer here is advantageous over having a static voltage divider?
Third: The active band pass filter used is slightly different than the band pass filters I see on google, so what does the resistor that is highlighted do?
Fourth: I want to increase the number of band pass filters so I can control more LEDs at different frequencies. To do this, I believe I would have to have a higher Q value and smaller band widths per filter, correct? How do I increase the Q of my filter so it is a smaller band pass?
Fifth: What is the point of this bit of circuit? Can't the op amp output go straight to the transistor?
Finally: They don't have transistor models marked. Since they are powering lots of LEDs, would you suggest a power transistor? Or maybe a darlington pair for better control?
Thanks in advance for your help! I really appreciate it!
EDIT: Quick followup question: Should I assume the VCC in the red squared part of the schematic is 12V as well?