My schematic is largely (read: almost entirely) based upon Casper Electronics' EchoBender pedal, which is in turn largely based on Tonepad's Rebote 2.5 Delay pedal, which is in turn, more or less, based upon the example schematic in the PT2399 datasheet. Having breadboard all three, I personally can not hear a significant difference in sound between the Casper Electronic version and the one on Tonepad, which some people say is superior sounding (the one in the datasheet just sounds flat). The nice thing about the Casper Electronics version is the inclusion of a feedback pot, which gives a really full sound to the echo effect.

The things that I have changed are a few mildly significant resistor and capacitor values. The biggest difference is that I have removed the "long delay" distortion pot. This potentiometer is basically forcing the chip to under-sample the input to create a longer delay and, in my opinion, doesn't sound very good. If you like under-sampled, long-delayed, audio, by all means throw in a large (1M) potentiometer in series with the delay pot. As you may have also inferred from this, the longer the delay, the less clear the output signal; so be warned that even the "short delay" starts to degrade when cranked up all the way.

For redundancy sake, I have redrawn the schematic. I have put three image notes on my schematic to indicate parts of the circuit that have changed. The schematic drawn by Casper Electronics is much more clear and I recommend you mainly go by that one.