**Audioguru again**

sent me this picture in my last Post:

I will be using the method at the bottom right Corner, since my Summing Amplifier circuit looks like that:

I also added a Line out, which shouldnt really be a Problem at all, right?

So if i now use the Method, Audioguru sent me a picture of, I have to use a coupling capacitors between the 10k Ohm resistors behind the Signal channels and the inverting opamp input, right? The opamp i want to use is the TL072 . It has got an extremely high Input impedance in the height of Gigaohms or even Tera ohms, if i remember correctly, so i dont have to look at this when choosing the Capacitor.

I saw a formula at a website that describes, how to choose that capacitor, but i have to know the input impedance of the Circuit. The formula then is:

C=1/2_3.14_f *Xc ( I dont know what "_" should mean, please explain if you know )

What is the input Impedance of that Circuit, i want to design?

That's just for the first, i will come to my other Questions after i understood This.

Thank you in advance,

Greetings