Reactance is like resistance in DC circuits: it opposes current flow.
Yes but the vital difference between a reactance and resistance is the phase between voltage and current. So you can not simply say that the more current current flows. When you add the resistance and reactance together it is a vector addition with a vector product. Here it is not the individual voltage and current at any instance but you have to consider the real power and the phase angle of the power.
I am not sure what point you are trying to make because current flow here is so small it is not an issue.
Because I understand so little about AC circuits, will those capacitor capacitance changes have any side effect I should be aware of?
I mean, I thought that if we were connecting the arduino ground to the opamp power supply virtual ground we would have had a +/-5V output rather than a 1-11V...
Yes, the op-amp is biased at 1/2 of supply.The output deviates from that 1/2 Vcc.With a 12V supply and no signal, the op-amp's output is a 6V DC level.A 2V p-p signal's crest would be at 7V and its trough would be at 5V.
What I don't understand is why we bias the input at 6V and then drop that 6V bias at the output instead of using a 0V bias and get an output swinging above and below 0.
In other words, wouldn't be simpler to connect the arduino ground to the virtual ground and remove C4? This should improve stability of circuit response at different frequencies as the op amp output impedance will have a null imaginary component (no reactance, just resistance).
I made the point before: two 1K resistors between +5 and Gnd, their junction is "virtual ground". With that as "reference" your DVM tells you that there is +2.5V above and -2.5V below. Then connect "virtual ground" to circuit ground and what's the result?
I can't see the difference between those two circuits. You have a ground symbol in a different place on both circuits but to what end. Both supplies, 12V and 5V, are floating so what you connect to the physical ground makes no odds.
Are you mixing up this symbol with a signal ground or signal common? ( both the same thing )
believe my only choice is to avoid the DC decoupling by using direct coupling,
Anyway whatever words you are wrong. Quite simply you do not DC couple audio signals and you have to avoid getting DC into a microphone to avoid distortion and damage.
You either use bigger capacitors or larger resistors or both. The frequency response is governed by the time constant of the resistor and capacitor. That is simply the product of the two values is equal to a time called the time constant. The fact that this might give you bigger physical capacitors that you want is just tough.
You suggested to avoid bigger resistors as it would make the circuit more susceptible to noise...
I understand that, but can't I directly couple on the Arduino side?