--- Tone stack mods ---
Q: I want more "roar" instead of "buzz"/sizzle/chainsaw! And i want more low end!! Please
A: Well, if you want a more "roaring" sound instead of a chainsaw-like buzz, you need some way to decrease the amount of high mids in your amp. Luckily enough this is easy on most amp that have a traditional tone stack.
There's an easy way to add in low end too. It won't make that much of a difference if you tune to E standard, but if you tune to B or use a seven-string it will make all the difference in the world. Be warned that this mod also lets you scoop out your mids a tiny bit more, so if you usually run mids on 4 run it on 4.5 after the mod.
What you need to decrease the value of the treble capacitance in the tone stack and increase the bass capacitance.
The following example is from the 5150, since i did this exact same mod today on my 5150.
The treble capacitor in this tone stack is a little strange, there are actually two of them. There is one that's 470pF, and one 100pF wired in parallel with the 470p. When you parallel wire capacitors the capacitance increases, so total capacitance of the treble caps is 570pF. This is a very large value and it accounts for a lot of the chainsaw-like sound of the 5150, the amounts of high midrange is absolutely insane. What you need to do is decrease the vaue of the capacitor(s). The first thing to try on the 5150 is to just cut the legs of the 100pF and remove the whole thing from the circuit, reducing the capacitance to 470p. This is still pretty high, but might just be enough for some (it was enough for me). The treble caps in the 5150 look nothing like ordinary caps, they look just like resistors. They are blue and located between the treble and the mid control. The 100pF one can be identified by it's color code, it starts with a brown ring. If you can't be bothered, well it's the one closest to the mid control. Just cut it out and see if you like it. If it's not enough, cut the 470p out of the circuit too and try soldering a 330pF or 220pF in it's place. 220pF is as low as i would go, below that you would lose a lot of aggressiveness! Remember to cut the legs off the components as close to the component body as possible so you can solder the new components on the existing legs (so you don't have to screw the main board out! saves a lot of work).
To add low end, look just above the treble pot for a small, yellow capacitor. It's right next to a jumper (a jumper is just a bare wire). Cut the bastard out (the stock caps suck ass by the way), remember to leave the legs of the components there! I would just clip the fucker in half so the legs are longer. Now, solder a capacitor on there. I used 100nF (or 0.1µF), you may experiment with 47nF, 68nF, 100nF, 150nF and 220nF. There is hardly any difference between 100nF and 10000nF so i wouldn't bother with anything higher than 100nF (the tone just gets more scooped after 100nF), and if you find there's too much bass after the mod try a 47nF. This is a huge improvement if you like to play 7 strings or tune lower than D, the low end chugging will kick ass after the mod.
Note: as always, use polypropylene capacitors. For the treble caps you can use silver mica, they're good too. I like Xicon brand polypropylene caps, they're inexpensive and sound great. Other favorites are Orange Drops and Mallory's, but i can't really hear the difference between an Orange Drop and a Xicon, and the Xicon costs 1/3rd of the price.
See the attached image for details
The procedure will be similar for all amps with a similar tonestack.