Converting a headphone output to line level
We have to assume what your Headphone output is.

If output is 5Vpp is being reduced to  1Vpp (-9dB Vrms) to a 10kohm line input, it needs 3 resistors to make a mono L-Pad.

2k2 (left) +2k2(right) to 800R to ground or 1k Audio pot.







simulate this circuit &ndash; Schematic created using CircuitLab