Simple LPF for Fuzz Face

[Mr.Kite]

We all already know the "EJ mod" for FF, a 100k vol pot. This one is interesting because might seem a minor mod, but the impact on the circuit is quite relevant:

- The HPF formed by the output cap and the vol pot gets altered, cutting more bass.

- The output impedance of the pedal is much lower, resulting in more treble and a more "stable\strong" signal to feed your amp and\or your pedals, substantially a better buffer over long(er) cable runs.

But what about if we want the original warm\smooth FF tone and less tonal interaction with other pedals?

As we all know, the FF isn't a very pedalboard friendly pedal in its stock form: it is very sensitive to whatever comes before or AFTER. Yes, after. Because in its stock form, the 500k vol pot is very high in value, and increases the out ompedance of the pedal so much that it becomes sensitive to cable capacitance and input impedance of the next stage, just like your guitar pickups.

This is in part why a FF sounds like a FF (a warm, overdrive-ish fuzz).

So, if we hook up our FF directly to an amp with a 1M in imp, through a 4,5mt cable we get one sound. If we hook up the same FF with the same settings to a 470k in imp pedal through a patch cable we get another sound.

To regain the original tone using the FF in a modern pedalboard we just need a cap between output and ground. If one knows the capacitance per meter of the cable to the amp, can calculate the cap value to regain the original tone. With "normal" cables I would suggest a 3-way switch with no cap, 680pf and 1,5nF to have a bit of flexibility (and an extra high cut\tone control if needed).

Or we can build a pedal like this one that I use for this application, but also to lower the frequency of the resonant peak of the pickups: it is a 12-position rotary switch, each position with a different value cap to ground. This way you can use it also with your vintage and valuable pedals without the need for any "invasive" mod... 

[Mr.Kite]

No one interested in this very useful mod?

[antonis]

Bad joke.. Sorry.. 

[Rob Strand]

No one interested in this very useful mod?

They are interesting and useful.  I guess I worked out that stuff out some time ago.

The effect of the cable capacitance on those old pedals with 250k and 500k output
pots is something that's overlooked for sure.  It's also why the old pedals don't
use an output filter, but, there's one hidden in the pot and cable capacitance.  Like you say it's not a reliable way to achieve that goal and all your mods help make the tone more consistent.