1kHtz?

I've been trying to replicate the voltage doubler (tripler actually) that is presented here:

http://youtu.be/I4ED_8cuVTU?t=11m

by alternating between

analogWrite(C9, 0.5, {freq:1000})

and

analogWrite(pin, 0.5, {freq:5000})

via the console but this isn't making a difference in voltage... I'm using 47uF Capacitors and regular diodes... I'll try replicating this again and sharing the result via video.