BillM, Do you have your tone control mod for the Excelsior available for sale yet?
Wow.I modded my Excelsior for faster tremolo. There were some songs that just didn't "play right" when you incorporate the tremolo beat into the tempo. It's an easy mod if you do it quick and dirty, and not much more difficult if you do it "right."
The speed pot is bounded by two 100K resistors, R21 and R37. If you make these resistors smaller, it will increase the maximum tremolo speed without affecting the minimum speed. You can do an easy top-of-board mod by soldering another 100K resistor across the leads of R21 and R37. Two 100K resistors in parallel gives you 50K, and lets the circuit oscillate faster.
The maximum speed, according to my meter, goes from 5.3Hz to 6.4Hz. That doesnt sound like a lot, but its a 20 percent increase. Using 82K resistors (effectively 45K) only gets you to 6.5Hz. I have 82K resistors soldered into mine, and Ill probably leave it that way.
Note that if you go too low or try to run without resistors, the tremolo circuit may not oscillate. Its fussy.
Just installed this mod yesterday on my amp. IT IS A MUST HAVE. Totally take the Excelsior to the next level. Especially with the pull up and raw tone. Seriously love it. Worth every penny.I finally came up with a tone control that sounds good and is easy to install. Nothing to clip, just two joints to solder. Pulling up on the control bypasses it completely and gives you the amp's raw tone.
The brown vintage-style Fender knob works for me; the difference in color isn't as great as it seems here:
As you can see, you can turn the upper chassis around and mount it, so the amp is easy to work on when modding. That Orange Drop peeking out is an experimental larger coupling cap from the phase inverter. It didn't make much difference.