Quick FF question for the smart guys

[tcobretti]

How does the value of the electrolytic cap on the emitter of Q2 affect the sound of the pedal?

[aron]

Just like any other capacitor in that situation. Smaller values cut more bass.

[tcobretti]

Why is it necessary?

[billings]

It's necessary because it gets rid of the negative feedback to the signal from the 1k resistance across the pot at high frequencies.  Take away the negative feedback and you get a large increase in gain, and fuzziness.

[aron]

As the Geofex article says, if you remove that, then yes, gain is reduced... a lot!

[brett]

Hi
The value of the cap is made large enough to be effectively zero in comparison to the resistance that it is bypassing.  Larger caps have less impedance to AC.
In the fuzzface, we want the cap resistance to be only a percent or two of 1k (the pot).  That will keep the bypass increasing until the control is nearly maxed.

Using the standard formula (Z (impedance, ohms) = 1/(2.pi.f.C)) we find that for f=440Hz and c=22uF, Z=16 ohms.  That's nice and low compared with the 1k pot, or even the resistance left in the 1k pot when it's at 90% (ie 100 ohms). 

The resistance to bass is higher (220Hz = 32 ohms), so in theory the byass of bass tapers off a little as you get to close to maxing the fuzz control.

cheers   

[tcobretti]

As the Geofex article says, if you remove that, then yes, gain is reduced... a lot!

Dammit, I freaking swear that I looked for the answer in RG's article before I posted!  I swear!