/diy/ - Do It Yourself

>>2702289
Batteries can be modelled as a voltage source in series with their internal resistance. In picrel, Vin is the unloaded voltage (determined by the cell chemistry) and R1 is the internal resistance. The load resistance is then modelled as R2.

It sounds muddy because you've not really made an attenuator.
That massive resistor is going to act like a low-pass filter in conjunction with the capacitance of the cable and recorder input.
You need to use a voltage divider to attenuate the signal instead.