The datasheet for the TDA1554 anplifier IC shows that its typical input resistance is 60k ohms and it must use an input coupling capacitor. The capacitor can be about 220nF which is a metalized plastic film type. The volume control can be 10k to 50k ohms per channel and should have an audio taper (logarithmic).
I couldn't find a photo of a volume control for me to mark the input terminal at one end, the ground terminal at the other end and the slider which is the center terminal.
The slider connects to the input coupling capcitor at the input of the amplifier.