FUZZ FACE: Output Level Mods

I noticed a topic on DIY Stompboxes about someone having low output issues on their Fuzz face, which seems to be a common issue.

There were a few suggestions that I like and have tried before, and while the Fuzz Face is one of the best-known guitar effects ever made, these mods don't seem to be common knowledge or well-documented.  None of these requires changes to standard layouts, which is a plus.

So here goes...  

• Take the 10n cap straight off the collector of Q2.    Result: this will be insanely loud.  Prepare to barely touch the volume control before hitting unity. 

• Flip the position of the 470 ohm and 8k2 resistors.  Result:   this will be just a little less loud than the insanely loud one mentioned above

• Take the output cap from the usual location, but adjust both the 470 and 8k2 resistor to a place where you are happy with the output level, but the combined values still add up to around 8k6.   Result:   this will give you an output level that you're happy with and is controllable 

A detailed analysis of all of the options mentioned above has not been provided, as they essentially all look the same on LTspice.  Same waveform & same frequency response - the only difference is the scale of the output voltage.

Why is this?  Because there has been no change to the resistance from the voltage source to the collector of Q2.  From the transistors' perspective, nothing has changed.  These don't form a filter with anything, so the frequency response stays the same.  

This is a spice sim, so all transistors and conditions are perfect, and germanium transistors are imperfect things - hence this post.  Your results may vary, is what I'm trying to say.

STOCK FUZZ FACE OUTPUT

Probably should start with a stock version as a reference.  Everything is set to full, and there's a healthy output level.  Happy days...  but not all Fuzz Face stories have happy endings, so read on.

200mv peak to peak in, about 430mv out

Here's the frequency response with the fuzz swept, which is how I'll do the rest of the comparisons.

And here's the standard schematic that we probably all know by now - note the voltages for comparison later.

R2 & R3 SWAPPED

A simple swap of R2 & R3 will increase levels quite dramatically - note the voltages compared to the stock schematic.

They look the same right - yes they do, but note the difference in scale on the voltages.  Now the output at the junction is a tad over 7 volts.   

The frequency response looks the same as the stock version

R2 & R3 MATCHED

This time the R2 & R3 values have been balanced - again, note the voltages compared to the stock schematic. 

Looks familiar right?

Now the voltage at the junction is about 3.5 volts - still very large, but only half of the method above.  But with a bit of experimenting or the use of trimmers, you can fine-tune this to a place that you're happy with.

I always like to question how much output a pedal really needs, as it seems to be a thing for modern pedals to have more output on tap than anyone would ever use.  Is all that unused gain just additional noise and a poor gain structure overall?

STRAIGHT FROM Q2

This is the nuclear option - this compares the stock output to straight off the collector.   It's massive by comparison.

CONCLUSION

So in conclusion - if you have low output Fuzz Face but really like the sound (which means you probably like the bias), maybe try one of these tricks before adding a trimmer, which will change the bias to Q2, and subsequently, the sound of the Fuzz Face.

This does completely ignore Q1, but this post was never intended to cover every possibility of the Fuzz Face.