Series resistance in Fuzz Face?

[polifemo]

I've been messin' around with lowering the signal in a SI/FF by using series resistance here and there.
Right now I've got a 10k resistor at the input, another 10k between Q1 and Q2 (from Q1 collector to Q2 base) and finally 22k between the Q2 collector resistor and output cap.

Sounds fine, but I'd appreciate some input regarding individual values/total series resistance values in a circuit like this!

(Yes I could use lower hfe trannies, but I want to experiment with this a bit :-)

[Davelectro]

Yup, this circuit is very sensitive to input resistance. With more resistance the gain decreases and at the same time you get more highs, as you probably know. The thing is you may end up getting a really good sound out of it, but it won't be a fuzz face anymore.

It's fun to play around with FF type circuits. I did it for years. But nowadays I'd rather look into a better design (i mean better input impedance, less noise, no specific transistors) than try to mod this thing forever.

[polifemo]

Thanks.

I've been trying to get something together that sounds a little bit like this "BC109-pedal":

https://www.youtube.com/watch?v=2wjFYodOcXw&feature=player_embedded
https://www.youtube.com/watch?v=8sbYfIHpCVk&feature=player_embedded

Not the fuzziest of fuzzes, but nice!

One needs a lot of clarity out of the pedal, and series resistance and/or series resistance with bypass caps seems to be one way to go.

[GibsonGM]

Yup, this circuit is very sensitive to input resistance. With more resistance the gain decreases and at the same time you get more highs, as you probably know. The thing is you may end up getting a really good sound out of it, but it won't be a fuzz face anymore.

It's fun to play around with FF type circuits. I did it for years. But nowadays I'd rather look into a better design (i mean better input impedance, less noise, no specific transistors) than try to mod this thing forever.

Yeah, +1.  You kind of NEED to have a good fuzz, but after a point, it's time to move to circuits offering more clarity, IMO.

Upping in input resistance of a FF will increase the input IMPEDANCE, and will make it more friendly to pedals that come before it...a nice side benefit to your experiments, Polifemo....

[Gus]

If you look around this site you might find the three transistor fuzz and rocket schematics
Input buffer before the FF like section with a selected input resistance and high pass frequency.

A ff type circuit has an non perfect input summing node
Look at Rin at the inverting amp section of the following link the RLC of the guitar or bass and the input cable is Rin with a FF.  The first stage of a FF is an inverting amp the emitter of the 2nd stage is a Vbe drop lower than the collector.
Rf is the feedback/part of the first stage bias resistor in the FF (47K, 100K etc)
http://en.wikipedia.org/wiki/Operational_amplifier_applications

This is part of the fun with the FF like circuit, where the first stage transistor is setup defines the first stage's openloop gain and how it changes with signal level

[polifemo]

Thanks for the replys!
They are much appreciated 

Any opinions about the resistor values I'm using (10k/10k/22k)? That's 44k all together.

A Sun Face has a 50k trimmer up at front and the Easy Face has a 250k pot (after the input cap) so I figured that 44k wouldn't be "too much".

[zombiwoof]

I have a Hartman Germanium Fuzz Face, that has Volume, Fuzz, and Level controls.  The Level pot is an input level control.  When I use it, I follow Hartman's suggestion to max the Volume (out put volume), put the Fuzz wherever I like it (usually maxed), and only bring up the input Level pot to slightly above unity gain, this makes the FF sound great without a wah in front of it, it cleans up when you turn down the guitar volume, and if you put a wah in front it works great without any oscillating or other problems that people have with a wah in front of a FF.  It also allows you to make the fuzz sound good with a humbucker guitar.  This to me is the answer to all of these Fuzz Face problems, I suggest instead of a fixed resistor on the input, put an input pot or trimmer in, I don't know what value the input Level pot is on the Hartman FF, but it works great.  The variable input level pot makes the FF work with any guitar output, a fixed resistor might work for a Strat but not an HB guitar.  I no longer have to worry about modding my wahs to make them work in front of a FF, as has been said this is a problem with the Fuzz Face, not the wah.

Al