Boost into fuzz face

[mills]

Sorry if this has been covered before, I read lots of stuff that skirted around the topic, but didn't see much of an outright answer.

I was thinking about building a fuzz face, but I'd wanted to put a boost in front of it for whatever reason.  I like my mosfet boosters, so I'd been leaning toward something like that.  I'd seen people mention that they put a boost into a fuzzface, but I always see that fuzzfaces don't like buffers in front of them.  Is there some kind of trick to making this work?  Should I just toss Jack Orman's transformer pickup simulator in the middle and call it a day? I think that the box I was going to use should be more than large enough.

My reference right now is pretty much playing with my woolley mammoth (sort of fuzz face derived i think) and a mosfet booster, and its not that it sounds terrible, but its a hint more sputtery and compressed even with the boost at unity gain. 

So My questions are:
     1) is there a trick to making a boost work going into a fuzz face?
     2) If there is, is there any boost you particularly recomend?  I play bass so probably no treble boosters...
     3) If I'm going to potentially toss a bit of low pass filtering in the boost stage, do I loose any possible benefit of a mosfet boost?
     4) Should i just suck it up, change my goals and build a tonebender instead?
     5)  If I have an appropriate trimpot value for each transistor, in the fuzz face portion can I theoretically swap from Ge to Si trannies with just the two adjustments?

Thanks for reading!

[Satch12879]

Why boost into Fuzz Face exactly? I don't necessarily think you could even "overdrive" the fuzz circuit anymore than it already is with a booster, because it's heavily into very weird clipping to begin with.  Also, there's going to be horrible noise.  Why not after the fuzz?

[mills]

For the why, I'd played with a friends fuzz face clone that had some bias controls to get gatey, choked sounding fuzz, and putting a boost before it meant that I could get those sounds without cutting off the sustain too much.  Might be weird, or not the best solution, but thats about how it worked.  Similar result with my wooley mamoth and the gate control, but I think thats more complicated than the usual bias change and not something that one could discuss on here.

Also, I found that there was a little extra fuzz to be wrung out of the circuit with some minor boosting going into it before it got too wierd.  I figured that the mosfet boost is pretty much unity gain to way too much boost, so build the fuzzface with a gain trimpot set to 60 or 70%, then have the mosfet boost wired with a pot as the overall gain control.  That way I can get that little bit above max gain most of the time, crank it for angry dirty sputtering, and crank the gain and play with the bias for my gated fuzz needs.

I guess there might be a more elegant way to do it, but thats my train of thought.  I'd not gone with a tonebender as all the things I'd heard didn't really sound exactly like what I was hoping to end up with. Sounded fuzz face-ish, but still not quite.  I'd just assumes that the extra gain stage up front in that was distorting too and that sort of smoothed or mellowed things... (Hopefully I don't sound like an idiot there, just no hands on time with a tonebender)

As for the horrible noise, is it just the "can't overdrive a fuzz more" thing, or could I expect something more?  Am I better off with a "dirty" boost to get more distorted and have the sputery gated stuff I was looking for?

[Dragonfly]

You essentially have a Tonebender.

This has definitely been done before... several examples in my gallery, Joe Gagans "Skyripper", Fuzz Factory, etc, etc, etc...

A search for "boost" and "face" (match ALL words) should give you lots of info.

[mills]

That simple, eh?  I'd been looking at lots of those options and spent hours reading aobut peoples fuzz face variations on here, and I guess i just couldn't really understand what it was that those circuits (the tone bender, that seven fuzz that I think was your design, etc) did that seemed to let the boost work out in front of a fuzz face without sounding bad.  I think that the mixed results of "my fuzzface won't work with _____ booster in front of it" and "my fuzz face sounds great with (some other) booster in front" made me wonder.  I guess if its essentially tone bender and I know I tonebender works then building one of them is probably the answer that'll give the least cursing and troubleshooting! 

Thanks for the suggestions and taking the time to help a confused new guy though.

[Dragonfly]

boosters can be useful "before" and "after" FF style circuits...

before - gives you some more gain, saturation, etc

after - gives you "more" of the fuzz sound..fatter, bigger...

theres a lot that can be done with simple building block circuits.

buy a breadboard - build a jfet boost, a bjt boost, and a mosfet boost ...also, build a fuzz face...experiment with different combos.

[ambulancevoice]

hmmm
maybe, try putting an 1n4148 in front of the fuzz face's q1
then try the boost in front
put the diode like this (maybe the other way around if your using a germanium pnp fuzz face)
http://www.diystompboxes.com/analogalchemy/sch/antiquity.html

[Gus]

No tricks to use a booster to a FF type circuit: However you need to understand how a two transistor FF Q1 feedback network works with the SOURCE resistance inductance and capacitance(the passive guitar or bass)With a buffer gain stage you can lose the guitar/bass interaction with a buffer or gain stage unless you add more parts.

The thing to note is the output resistance of the booster low resistance output tends to have the problems a 10K output resistance is a good place to start IMO

In the three tran(In schematics link at the top of this page) I used a EF so I added a 10K in series with the fuzz section.

   With a transistor collector out circuit you need to read up on what the output R is.  A hint look for the Doug H. Hot Si schematic note the controlled gain first gain stage before the fuzz section.  Copying that fragment might be what you want.

[mills]

Thanks for the circuit and reading suggestions Gus!  I'd had a vague idea about in/output impedances but didn't even know where to start as to why and what a fuzzface likes to see at the input.  Spent a few hours reading old threads and re reading some great articles on geo and I think I'm getting towards a point where I might be able to make this work with a little preliminary tweaking (and posibly a few extra parts).  Learned a tonne about the fuzz face, and managed to get through the entire "technology of the fuzz face" article without my eyes glazing over or anything like that!

[Gus]

http://www.aronnelson.com/gallery/main.php/v/DougH/hotsi/GS_Tonebender.gif.html

Use the Q1 section fragment before your FF type stage.  You can use all types of Si small signal transistors for Q1 and Ges should drop in and be close.  The q1 part has a gain of about X10.  If a fixed gain stage as the first gain stage in a 3 transistor  boost FF etc type.   I find X10 gain a nice trade off between overdriving ,clipping the first stage and having good drive to the FF section.

  If you want the max gain and/or an EQ  boost at the first stage bypass the emitter R4 with a cap this can be say .1uf to 47uf as a good starting range or you can use an R and C..............

Anyone build the Hot Si?  Doug did some nice work with this circuit.

[bumblebee]

try a LPB before a fuzzface,it sounds cool imo.

[Gus]

  Yes the lpb can work but is it the "best" for what a person wants.  How you set up the sections gain has a lot to do with how the distortion fuzz sounds.  Do you want the first stage to clip a lot and then add to the next stage or clip less or not at all and drive the next stage harder?    What I posted has a gain of 10 that can be changed with a cap and resistor across the emitter R to a higher gain if wanted.  IMO it is a good starting point as the first stage of a three transistor fuzz (gain stage to FF type gain section type) then adjust to taste.   

A LPB is the same type circuit as the Q1 fragment: however the Q1 fragment was thought about for gain, input and output R and the ablity to use transistors with a wide range of Hfe as the boost before a FF type fuzz.
  The LPB has a different input R and gain than the Q1 fragment.  The use of the 1K helps the input R a bit.

The Q1 circuit fragment and the LPB are standard text book circuits you can find in books from the early days of transistors.

Things to read about to "design" the first gain stage.  Gain setting resistors,  input R (bias string and Hfe and emitter leg), Output R, Operation points and how the stage clips (don't get stuck at collector at 1/2 the power supply remember this is fuzz, distortion not a stereo)  ,   Hfe Vs Ic(collector current)