Geek » Fender Deluxe Amp Project
The Mods
After a few different players played the amp, with different bands, I got a chance to better understand it's characteristics, and it became apparent that I would need to fiddle with it some more to get it exactly like I wanted. I spoke with Bruce Collins at Mission Amps after searching around for ways to improve the Volume and Tone control issues inherent in the Deluxe. Bruce put together a nice package of bits and pieces and sent them to me with clear enough instructions that I only screwed up a couple of times.
Meet Mod #1:
Mod #1 is often referred to as the "Paul C" mod. As stated on a guitar amp forum, this mod is a "simple mod to the phase inverter where the grid is DC biased via a 2.2M resistor to the supply, and not referenced to the cathode. The result is a symmetrical clip."
In non-geek language this means that the amp has a smoother breakup at higher volumes with a slight increase in headroom. So it isn't as raunchy sounding when it's turned up loud and starts to distort.
This was a pretty straightforward procedure, with no screw ups. Three little changes in the phase inverter side section of the board.
1) I removed the 56k cathode resistor and replaced it with a jumper wire.
2) I removed the 1.5K bias resistor and replaced it with a 56k resistor.
3) I added a 2M2 resistor between the 1M grid resistor in the PI stage and the 22K dropping resistor in the power stage. In geek terms this is a "2M2 resistor from the grid of the inverter to the B+ rail used by the 56k plate resistor."
Meet Mod #2:
Mod #2 is called the "Bruce Collins Vol/Tone Mod." This one was a bit more involved, and required taking off all the pots and rewiring everything. It uses the same Volume and Tone circuit as the 6G3 Brownface Deluxe, with some added features.
There was a lengthy discussion about this mod on the 5E3 forum but it seems to have disappeared now. It was here. It does a better job of explaining it than I could.
The reason for installing this mod is pretty much summed up in this post by Bruce:
"The standard complaint I hear is: The amp ramps up super fast and breaks up very soon with not much useable range in the volume pots. The tone/vol mod fixes that and at the same time smooths out the response and volume curve. Plus it reduces the dark muddy tones as you play louder.
After this mod is installed, (about an hour job), both channels are a little brighter and more clear. The normal channel is finally useable and the bright channel is special with much better highs and note defintion, while the amp doesn't crank out until the volume pots are around 4.5-7 instead of 1.5 to 3."
Yes. The amp now has more control of the volume versus the tone, and you have more gain before it turns to distortion. Before, the channels sounded a bit "dull" by modern ears, and it would start to distort at like 2.5. Now there is a lot more gain to work with, up to like 7, making the amp more versatile for different players and music styles.
Definitely a cool mod. Please contact Bruce directly at Mission Amps for more info.
Meet Mod #3:
Mod #3 is currently sitting in the box until I find a day to drill another hole into the chassis between the preamp tubes. It's supposed to make guitars with humbuckers hum like motherbuckers.
I've never figured out whether it's pronounced "Moe's (like owned by one of three stooges) or Moss (like that guy out of Bonanza), but the one down the hill from me is open until 2am most days, which means that if I get out of the club early enough, I can catch the best burger in town, the muo si la bao or the Spicy Mos Burger. They have lots of jalapenos and 
