yep... and hopefully as high of gain as possible.
I've used the TO-220 darlington from R-Shack in place of the MPSA13, also try just single transistors. You can get a wide range of sounds from this, all depending on what transistor gain is.
If it doesn't have enough gain, make the resistor to V+ bigger. If it has too much, make that resistor smaller. I've found the best ranges for 2N2222 types to be between 10k-100k, and for darlingtons I've kept the range from about 4.7k-33k.
Have fun! Any more questions, pop back in... or just give us a progress report. I just came downstairs from about 2 hours of playing with the BF. Some people have a FF fetish, I can't put down the BF, lol. It's like my... BFF.