Stop giggling like a girl Robin :p Actually a capacitor on it's own is able to 'snub' out unwanted transient spikes, as it forms a simple 1st order filter. The problem is that PWM supplies the drive voltage in high frequency packets so it gets shorted by the cap where pure DC wouldn't.

I'm not sure what voltage to be honest as I never measured it. It is the supplied motor with a CNC3040.