Audio signals only go between -1 and +1. This is why you only get inputs 1 and 2, in that the ISWITCH only gets values between 0 and 1, without getting the 2 it would need to select the third input. The values you enter into the sequencer gets converted into audio-type values between -1 and +1.
You could use a C_MULTIPLY after the A_TO_C to extend the range. Multiplying by 2 would probably do it.
