As far as I am aware the voltage used by the Tuner module for its ADC conversion is 5 volts [certainly the Chip (PIC Micro) they are using for the ADC conversion in the module runs on no more than 5 volts].

The 22K ohm resistor referred to in the Developer Info Page is inside the Tuner module itself between the socket where the Sony Remote plugs in, and the PIC chip which does the ADC conversion.