Goodness. I! just! did! the! reverb mod!!!
on my early "no-stripe" Mk III!
I am flabbergasted with awe. After owning this amp for over 15 yrs and resorting to either digital or pretty weak and noisy verb during most of that, it finally breathes without a respirator! Literally a 5 minute job if you have the 3.3k/.5w resistor handy (I didn't) ... all of a sudden my Showman Reverb has a rival for my affections! It helped that in swapping around prior to doing the mod, I hit on a combination of preamp tubes that I really like, but the mod by itself was very dramatic in effect. Suddenly warm and clean. It still needs to crank up pretty high to about 7ish to where I like it, but the very thought that this amp would ever produce "too much" reverb even set at 10 is something I never thought I'd see.
So then I learned another thing about my III: the FX loop send is post-reverb! I would have never considered that, but its true. That means that no mod is necessary to tap the preamp signal out to an external power amp. Just remove your power tubes, and patch into the fx Send (stick a dummy plug into the fx Return jack).
I've just decided (because I just tried it and it's amazing) that I'm going to play my gig on Thursday with my Mark III combo preamped out to my Yorkville power amp, in turn feeding 250w back to the JBL in my Mark III
All of a sudden I like the Rhythm 2 "crunch" channel (for leads, in conjunction w/ OD pedal)! I'm in love with my Boogie again!