Nurse Quacky, why must you torment me?!

[Devius]

You know, I love this effect. It's true, I do.
I just can't for the life of me get the high e string engaged.

[Mark Hammer]

Stick a 39k resistor in series with a .0047uf cap, and place that in parallel with the 47k/.01uf pair.  That will increase the gain for stuff above 870hz a bit, such that the sensitivity is higher for strings that have less energy to contribute to detection.  If that isn't enough, use 33k and .0056uf.