The thing that many people miss when they discuss buffering a fuzz is that there are actually three components to effectively (i.e. transparently) buffering the input of classic Fuzz pedals. The "Big Three", if you'll bear with me:
1.) Placement
2.) Impedance
3.) Dynamics
Placement is tied to the magnitude of your input impedance. Placement is typically an issue because of the output impedance of the device directly feeding the fuzz. Impedance is tied to what the device "sees" before it. Dynamics is tied to the specific high and low end content of the device directly before the Fuzz.
Now I imagine some of you are asking: "Why are 1.) and 2.) different?" Let's use the Fuzz Face as our example for simplicity...
The most elegant, simple solution to all three of these issues is running it first. As a person sort of leading with his buffer design, I can still marvel at how this solution works 75% of the time. Running a fuzz first accomplishes the following:
1.) It merges Placement and Impedance issues because Placement is solved by being first in line and the Impedance of your guitar pickups is high enough not to cause a mismatch with the 0.5-1k or so input impedance of something like the Fuzz Face.
2.) It maintains Dynamics by keeping the guitar/fuzz frequency rolloff trick when you turn down.
So what the hell happens when we try to buffer a Fuzz Face? First off, if we simply introduce a high impedance buffer and nothing else, we only solve Placement issues. We solve this issue because now the input impedance is high enough at the input of the Fuzz Face that the output impedance of anything driving it is now irrelevant.
