If I had ten cents for every time that someone posted on a guitar pedal forum that it was bad to place a buffer in front of a fuzz pedal, I could go to Starbucks every day for a month.
First, they is no universal agreement as to what specifically defines a fuzz pedal. Even the effects manufacturers are not in agreement about it. However, most everyone agrees that the fuzzface design is indeed a fuzz, and that placing a buffer in front of one will change the sound. I concur.
I think we can all agree that a buffer will “change the sound” of a fuzzface but that does not automatically make it bad to use a buffer before it. Consider this, when a wah pedal driving a fuzzface gives trouble with oscillation or other disruptive sounds, what do the experts recommend? A buffer… a buffer after the wah and before the fuzzface.
Furthermore, one of the most revered boutique fuzz pedals in the Lovetone Big Cheese, the design of which includes an opamp buffer driving a fuzzface circuit! Does it sound bad? Not by the vast majority of its reviews.
So what is going on? My initial thought is that the warning about buffers before fuzz originated with players who like to roll back on the guitar volume to get some interaction between the guitar pickup and the fuzzface. It is true that a buffer interferes with this interchange, and I could see how some guitarists do not like that change. I don’t twiddle the guitar volume so it never bothered me.
After some thought on the design, it seems that another technical factor is involved. The first transistor of the fuzzface is the gain stage and the second transistor is a buffer which is providing the feedback to the inverting input of the first transistor. This is actually forming a crude inverting opamp stage, in which the guitar pickups impedance is acting as an input resistance. It is also the reason that different guitars can sound radially different with fuzzface pedals since their pickup impedance may vary greatly from each other. If a buffer is driving the input stage with a different impedance, and that can make it sound different.
Also, a Big Muff is a fuzz pedal and a buffer driving it will not have much impact on the sound. There is too much internal gain and the cascaded clipping stages will swamp out any minor differences caused by the driving source.
Does a buffer before a fuzz change the sound? Sure it does… a buffer will change the sound of almost any pedal it is driving but that is not automatically bad, even with a fuzz! It might make it thin or cutting but it might also give more clarity to your distortion sound. There is no way to know until you try it.
‘No buffers before fuzz pedals’ is one of the often repeated Internet myths that should be busted. It can sound good or bad, and much depends on you guitar, amp and the other pedals on your board. As always, let your ears be your guide!
