I've owned a couple Twin Reverb Fender amps [both silverface] and sold one of them to Jimmy Herring; a Jerry Garcia rig expert. As I remember, Jimmy wanted my 71' twin for the 2 JBL 120F's. He tried to just buy the speakers but I insisted on the unit as it was. He told me Garcia used other amplification to power his twin reverb cabs - but it might have been vice-versa?!? [used Twin to power other speakers?]. Having owned a couple, I don't think Fender Twin Reverb has a preout feature on it - though one very well may be fashioned by a tech?!? But whatever the exact details, Garcia used Fender Twin amps, JBL speakers, McIntosh, and some others; I think he or Lesh initially used an MC50 but changed to better and more powerful models as they came available through the years. Others may have been used, but MC2300's were the McIntosh model used in the wall of sound. Lots of touring bands in 70's/80's used the MC2300; George Jones comes to mind.
