Hi Randy
To be honest I don’t know why that the resistor is required, I just remember reading it in the paperwork for the CD adapter iPod stuff.
Infact on the very first SC1 that I bought, I purchased a resistor and connected it as described only to then realise the the complete APU 10 unit and its wiring / plug was missing. So removed the resistor as it was completely  unnecessary.
I remember feeling rather stupid when I realised it was missing.
Cheers Scudie