Please forgive any mistakes, errors or omissions some of this was done from memory and and referencing back to the manual.
This amp can be bought in Kit form "if you are proficient with such things"
Heck you can even get a Cab and start from the real scratch. Mine was sitting around for a while especially since I bought a MK-IV
Extra gain stage fir preamp
Fat switch function is doubled "more boost", uses foot switch only
Treble pot is now push pull for mid-range boost.
The master volume is now Torres "Dual Stage" provides slightly more tube overdrive if master is turned down, cleaner if the master is turned up.
Mid-range is mod-ed to have double the standard Jr. range.
Reverb modded to Tube and Transformer for more organic tone "NO CHIPS"
A greatly improved power supply (Torres "Cap Pack" power supply utilizing high value Caps for low noise and better bass response)
Preamp tubes are run on DC filaments for major reduction of noise.
The amp uses a Weber Copper CAP dual GZ34 rectifier which provides for features of dual rectifier tube and even that can be "self changed" with a solid state device for higher power and bass response.
Choose the speaker that fits your tastes because from my observation this "rebuild" (Has made a small amp great i.e. easy to carry, jam &
practice.) made this little bugger much more dynamic. It meets my tone preferences for what I use it for.
I am in no way professional musician. I just like what I like or expect to hear.
I just started a couple of years ago to re-learn Guitar after 25 year hiatus priorities are priorities.