I was looking at the back panel of this Fender Pro Reverb, and it has both Effects Send/Return AND PreAmp Out/In jacks. I was wondering what circumstances the Effects Send/Return would be used instead of the PreAmp Out/In. Or if there is a situation where both would be used? I also noticed the Effects Send/Return has a button that gives you a choice between Series or Parallel. Which is preferred under what conditions? I hope this isn't too stupid of a question, but my Peavey amps only have what they call EFX Send/Return jacks, and my Fender Hot Rod Deville only has what they call a PreAmp Out/In jacks. Neither have both EFX and PreAmp jacks, yet but both seem to have the same sound and tone when I insert an effect in the jacks. Is the signal for an EFX loop tapped from a different place in the circuit than for the PreAmp In/Out?