I've noticed that Amp6-Basic and Amp3 both have alternate Rin and Rfeedbk values for various input sources (MP3 player, General use, or Preamp with fairly high output signal). I don't see this mentioned in the instructions for AMP9. If I want to drive this with an MP3 player, do any of the resistors need to be changed for optimum performance?
Also, has anyone recently built one of these? The instructions imply that the toroid wire has changed from .6mm to .7mm, but the wire in my kit seems very thin and easy to wind, so I'm thinking it might be .6mm.