I have a digital piano without line output (not even earphone output) but I would like to record what I am playing. So I decided to convert the speaker level to mic level so I can record the audio in my smartphone (using the bultin TRRS input of my smartphone).
My piano speaker is 4 ohm and 10v. I need to bring it down to 0.01v (mic level? I think smartphones accept 0.1v?). A really smart and nice guy told me, in another thread (in which I had a similar problem), how to bring line level to mic level with this circuit:
It worked PERFECTLY! It has 10:1 attenuation and impedance of 1k which is the recommended to smartphones. Now I need to increase this attenuation and I know I can easily do this changing the 1k and 100 ohm resistors, however that will mess with the 1k impedance recommended to smartphone.
So how can I do this? Do you know the values of the resistors that I need to change (the capacitor will have to be changed?).