[sdiy] trouble driving cmos from modular signals

[dan snazelle]

normally when I interface a modular signal into a counter, 
say a +/-5volt VCO signal into a 40xx,  (in this case a 4017)


i put it through a resistor with a diode to ground, or a diode with a resistor to ground.
but i am working right now with a 4017 which WILL NOT 

see the VCO output unless I put it through a level shifter module first and add a bunch of gain.


i would LIKE to find a passive solution  to this predicament,  but I am not sure if that is possible.

(maybe 2 diodes and a resistor?)
                                                                                                                                                                                                            


THANKS FOR ANY HELP!!!