Re: Amp distortion + fuzz pedal = ?? (Not clear on fuzz use)
Fuzzes sound great through old style non master volume amps like JTM marshalls, twin reverbs, dual showmans etc. To really get the massive tone and rich harmonic colour you need plenty of headroom. Fuzz is a world of its own and needs a completely different approach to what you might use with a high gain amp or even how you use overdrive pedals.
I agree with Gibson here.
There are many pedals called "fuzz", but other than an intense square clipping of the signal, they don't have much else in common. The two "classic" fuzz types that many refer to are the Fuzz Face/Tone Bender styles and the Big Muff style.
Big Muff: nearly always needs to be run into a clean amp. The amp's natural EQ profile should compliment the EQ of the specific muff. The classic Muff tone stack is a huge mid scoop, and it needs a pretty mid heavy amp EQ to sound good. Otherwise you risk having no mids and harsh treble. A ridiculous amount of "boutique" fuzzes are now based on the Russian Muff (bigger bass than the original) that they modify for more midrange allowing a wider range of natural amp EQs to work with them.
Fuzz Face: Nearly always works better with an amp that is at least compressing, if not distorting. (Now I don't mean 5150 or ENGL distorting, I mean a light Plexi crunch distorting). The nature of these fuzz pedals is that they generate a lot of high harmonics due to the square clipping. The compressing, rolled off tone of a breaking up tube amp compliments and limits these harsh harmonics and you get the classic smooth yet raspy fuzz tone we know and love.
As others have mentioned, an overdrive can be a secret weapon when dealing with fuzz, especially if your amp is not the ideal candidate for a fuzz. The classic overdrive circuit:
-rolls off bass
-adds midrange
-rolls of treble (if desired)
-adds soft clipping
By pairing an OD with a Muff, you can fill out those midrange frequencies that missing. By pairing an OD with a Fuzz Face you can smooth out the harsh high harmonics and reduce the bass of a germanium fuzz face. Try different ODs before and after the various fuzz pedals to see what works best with your guitar/pickups and amp. Also remember to back off the volume on your guitar with Fuzz Face and Tonebender type circuits. That can function as an awesome overdrive type tone as well!
This is coming from a "classic rock" type view of fuzz. When you get into alternative and modern rock styles, the rules go completely out the window, and ANYTHING goes!
Finally, remember that fuzz is a nasty effect. It's supposed to be uncontrollable and wild. A Tube Screamer into a Blackface is a very polite, neat and controlled sound. Fuzz needs experimenting to get the most out of it. Have fun on your journey!