Hey there. I know I've seen this on the board somewhere, but I searched and searched and skimmed and skimmed and couldn't find the answer.
My CA-9100 has a small blue switch next to the volume knob. If I remember correctly, when it is not depressed, the "4.7Kohm resistor mod" is not engaged. Or said differently, when the switch is pushed in, the 4.7Kohm resistor is engaged.
Is that correct?