Quick question about GGG buffer

[Bobv]

quick question about this: http://generalguitargadgets.com/pdf/ggg_buffer_jfet_sc.pdf

What exactly does the 3.3k resistor do, and how vital is this value? I only have a basic understanding of audio circuits in general, but it doesn't look like any important biasing resistor. (Looks like pulldown or whatever it's called, but much lesser value.) On the breadboard i don't notice much of a difference between 4.7k and 2.4k

[petemoore]

  Chosen for it's ability to allow the source to swing +/- a good ways without hitting or getting near a power rail.
  Geo has the Jfet bias info.
  See if source voltage bias point moves up using larger value source resistor...