Cookbook Fuzz (review)

[Dragonfly]

In my experience with Muff Fuzz type circuits, the 10K resistor at the input does not provide enough impedance and the circuit sounds too woofy.  

i changed the "stock" value input cap from a 1uf to a .1uf, thinking that it would help compensate for this...good thinking, or wont work?

The stock MF uses a 100K there and Gus' mod's uses a 220K.  This will make it sound more like a distortion and less like a fuzz.  Of course a 250K pot there greatly increases flexability.  Should sound really good.  

using it as a "pregain" control, sort of? 250k pot, with input to lug3, output from lug2, and lug1 open?  or do you think it would be better to take a 22k (or so) resistor to ground from lug1, so it doesnt cut signal completely?

Just a suggestion, but you might try the GE's and the SI's reversed, because the first stage isn't going to have as much juice going thru it as the second.  I think you will need the lower clipping threshold in the first stage.  

good idea...i hadnt considered that. shottky's might be interesting in place of the germaniums as well....

also, in playing around with opamps, ive hooked up a pot as a variable resistor from the 9v+ lead to the Vcc pin on the opamp...helped get a wider range of sounds...might be interesting in this circuit...sort of a voltage starve deal.

also, could hook up dpdt switches for diode selecting in the second stage...selecting from led or silicon, or both...

interesting circuit, that could turn out pretty cool.

thanks for your input !

[Dragonfly]

heres the latest schematic revision, which includes some great ideas from Mark Hammer and WGTP. ive included a simple "voltage starve" circuit in the upper right hand corner...it hooks to pin 4 of the opamp.

anyway, hopefully we'll keep the ideas flowing...you guys rock, and youre definitely helping in my education about opamps !

so...were up to 6 knobs...(pregain, starve, gain 1, gain 2, low pass, and master volume).....anyone wanna go for 7

[jmusser]

Since I kind of have this half way done to start with, I may as well go the whole route and see what the added op amp does for it. I believe, I'd like to keep my first section with the LEDs in the feedback section, and then have another stomp switch to engage the second stage for lead work. All I have to do now is get a wheel barrow to hold all the pots I'll have to have! This ought to be intersting Thanks for all your work on the schematic, it's cool to watch it evolve. I still have the Dirty Sanchez & Joy Buzzer to build.

[Peter Snowberg]

so...were up to 6 knobs...(pregain, starve, gain 1, gain 2, low pass, and master volume).....anyone wanna go for 7

Hehehe....


Here are two ways.....

(1) go back to separate bias circuits, except make the second one out of a 100K resistor and a 100K pot. That will give you gated sounds and will work in tandem with the 'starve' control to adjust breakup.

(2) add a 250K linear pot between ground and a pair of inverse parallel Schottkys which are then connected to the signal input like a 'black ice' fuzz. With single coils that adds some compression (just a tad) and grit to the attack. It gets rid of a lot of trebble coming in which allows the effect to provide most of the high frequency content. DDD used this trick in one of his designs.

OK.... that's 8

[Dragonfly]

Since I kind of have this half way done to start with, I may as well go the whole route and see what the added op amp does for it. I believe, I'd like to keep my first section with the LEDs in the feedback section, and then have another stomp switch to engage the second stage for lead work.

you could also use a 3rd stage w/ no clipping diodes or led's, simply to "boost" the sound of the first 2 stages...   :shock:

All I have to do now is get a wheel barrow to hold all the pots I'll have to have! This ought to be intersting Thanks for all your work on the schematic, it's cool to watch it evolve.

im kinda hoping it'll take on a life of its own and everyone will keep adding to it. it seems like an interesting platform for experimentation and learning.

I still have the Dirty Sanchez & Joy Buzzer to build.

:twisted:

the sanchez is "all out nasty", and the buzzer can be a bit more versatile...but its not as "sick"...    i like 'em both quite a bit....

[Dragonfly]

so...were up to 6 knobs...(pregain, starve, gain 1, gain 2, low pass, and master volume).....anyone wanna go for 7

Hehehe....


Here are two ways.....

(1) go back to separate bias circuits, except make the second one out of a 100K resistor and a 100K pot. That will give you gated sounds and will work in tandem with the 'starve' control to adjust breakup.

so my "guess" is that this will cause an "adjustable bias" for the 2nd stage ? hmm...could be pretty cool....

(2) add a 250K linear pot between ground and a pair of inverse parallel Schottkys which are then connected to the signal input like a 'black ice' fuzz. With single coils that adds some compression (just a tad) and grit to the attack. It gets rid of a lot of trebble coming in which allows the effect to provide most of the high frequency content. DDD used this trick in one of his designs.

OK.... that's 8

i'm not sure i'm following...i'll have to check the black ice schemo....

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for about a minute i had considered adding a pair of diodes to ground between the stages, with a switch to activate them....then i got sane....  :twisted:

[Mark Hammer]

Shaping up nicely.

The 2.2uf output cap, or rather the output feedback path, is located wrong.  The connection to feedback should go to pin 7 directly, rather than to the far side of the 2.2uf cap.

The recommendation to have lower threshold diodes earlier in the chain that higher threshold ones is absolutely sound.

The input resistor labelled Pregain may or may not be important.  My sense is that it may be useful for SOME op-amps but not for a great many others.

Note as well that the effect of the Fuzz Depth 1 control will depend on the setting of the Pregain control.  With Pregain set to max resistance, maximum gain on the first stage is around 2, generally not enough to produce any clipping, even with Ge diodes.  You can get aroud that by using a larger value feedback pot in that stage (e.g., 1meg) but the problem that creates is that it will be a twitchy pot if you use lower/smaller Pregain settings.  

Without wishing to diss anyone, my own sense is that the Pregain control is not really needed, at least not in any final build.  Perhaps just as important, it will be very hard for you or anyone to identify an optimum Pregain setting.  It just MAY have an influence over distortion characteristics, as suggested, but since changing it also changes the gain (reducing it) and LIKELIHOOD of clipping, it will take a LOT of Pregain/Fuzz-Depth tweaking to figure out what setting produces the desired quality of distortion.  Besides, if it isn't fuzzy enough fo you, there is always stage 2.  If there WASN'T a stage 2 then I'd agree that some consideration needs to be given to the stage 1 input resistor, but at this point it's a bit like worrying about the angle you cut the parsely bits at in a 10 gallon pot of soup - once you stir, it doesn't matter.

I may not have been articulate enough about the Tone control.  One of the interesting properties of wqhat you have here is that you can set each stage for just a hair of clipping and coloration.  When the gain is set low enough in each stage, it should function as a *somewhat* clean booster with fairly wide bandwidth.  Under those conditions, the tone control will have a clearly audible effect as you adjust it.  Once the gain gets cranked, though, because the rolloff of each stage will decrease with greater gain, the tone control wil have a less discernible effect.  Not a crime or weakness, just something to be aware of.

[Dragonfly]

Shaping up nicely.

The 2.2uf output cap, or rather the output feedback path, is located wrong.  The connection to feedback should go to pin 7 directly, rather than to the far side of the 2.2uf cap.

d'oh !!!  error in drawing...for some reason i knew where to put it, but i drew it wrong...dang late night bleary eyed paint sessions
(its now its proper place on the schemo)

The recommendation to have lower threshold diodes earlier in the chain that higher threshold ones is absolutely sound.

i thought it to be a great idea as well...

The input resistor labelled Pregain may or may not be important.  My sense is that it may be useful for SOME op-amps but not for a great many others.

Note as well that the effect of the Fuzz Depth 1 control will depend on the setting of the Pregain control.  With Pregain set to max resistance, maximum gain on the first stage is around 2, generally not enough to produce any clipping, even with Ge diodes.  You can get aroud that by using a larger value feedback pot in that stage (e.g., 1meg) but the problem that creates is that it will be a twitchy pot if you use lower/smaller Pregain settings.  

Without wishing to diss anyone, my own sense is that the Pregain control is not really needed, at least not in any final build.  Perhaps just as important, it will be very hard for you or anyone to identify an optimum Pregain setting.  It just MAY have an influence over distortion characteristics, as suggested, but since changing it also changes the gain (reducing it) and LIKELIHOOD of clipping, it will take a LOT of Pregain/Fuzz-Depth tweaking to figure out what setting produces the desired quality of distortion.  Besides, if it isn't fuzzy enough fo you, there is always stage 2.  If there WASN'T a stage 2 then I'd agree that some consideration needs to be given to the stage 1 input resistor, but at this point it's a bit like worrying about the angle you cut the parsely bits at in a 10 gallon pot of soup - once you stir, it doesn't matter.

hmmm...more thought and experimentation required...

I may not have been articulate enough about the Tone control.  One of the interesting properties of wqhat you have here is that you can set each stage for just a hair of clipping and coloration.  When the gain is set low enough in each stage, it should function as a *somewhat* clean booster with fairly wide bandwidth.

that was my thought as well...

Under those conditions, the tone control will have a clearly audible effect as you adjust it.  Once the gain gets cranked, though, because the rolloff of each stage will decrease with greater gain, the tone control wil have a less discernible effect.  Not a crime or weakness, just something to be aware of.

noted...

[Dragonfly]

(2) add a 250K linear pot between ground and a pair of inverse parallel Schottkys which are then connected to the signal input like a 'black ice' fuzz. With single coils that adds some compression (just a tad) and grit to the attack. It gets rid of a lot of trebble coming in which allows the effect to provide most of the high frequency content. DDD used this trick in one of his designs.

OK.... that's 8

ok...i checked the schemo on the black ice...easy enough to implement...think it'd make a fair difference to the sound?

[WGTP]

Check out the Mockman at ROG.  Gary used the pregain Pot on that.  He also leaves at the 10K resistor between stages, which really incresese the drive, but I'm not sure what it does to the frequency response

It in effect the 250k pot is a bass boost with a .1uf cap.

What happens is interesting in that lowering the pot reduces input impedance, raising the bass input to the op amp, but with a .01uf cap it also raises the bass cut off frequency lowering the bass input, so what you end up with is that it starts getting very mid-rangey.

Gus' use of a 220K at input and 1 Meg in the loop reduces gain to where it may not clip with the diodes in the first stage, but the signal is nicely voiced to distort the second stage.   :twisted:

It depends on what type of sound your after, as always.

Another suggestion:  Split the 10K resistor between stages into 2 - 1K's and add 2 SI diodes to ground in between (sort of like Mark's Rosey Ray). Put a 5K pot between ground and the diodes for some adjustment (and an extra pot) like the HMP.

Might as well add a 3rd stage.  Looking good.  

[Dragonfly]

Another suggestion:  Split the 10K resistor between stages into 2 - 1K's and add 2 SI diodes to ground in between (sort of like Mark's Rosey Ray). Put a 5K pot between ground and the diodes for some adjustment (and an extra pot) like the HMP.

yep...thats pretty much what i'd mentioned in an earlier post as a possibility, but im not sure how much affect this would have to the sound, especially at higher gain settings...

thoughts?

Might as well add a 3rd stage.  Looking good.  

im actually trying to decide whether to make a 3rd or 4th stage, and if they should be clean or clipping stages...

really a very interesting circuit so far...

i decided to keep the pregain pot for now, so i can assess its value at "build time"...i want to get this thing completely designed before building it...maybe once its built i'll donate it to Aron for a raffle or something...just something to help offset some of his expenses in hosting this great forum ...

[Peter Snowberg]

...so my "guess" is that this will cause an "adjustable bias" for the 2nd stage ? hmm...could be pretty cool....

Exaqctly.

Some will like thiese sorts of sounds and some will not. Let your ears decide. Adjustable bias in a transistor feedback circuit will lead to instabilities that an opamp circuit will not produce, but then a mis-biased opamp will produce sounds that a mis-biased transitor won't.

ok...i checked the schemo on the black ice...easy enough to implement...think it'd make a fair difference to the sound?

I have such a diode pair in my Strat and I really like what it does when the pot is turned up to about 30-40%. It works like a treble control to a degree, but rather than just eliminating the treble, it replaces it with some crackle. I don't use my regular tone control any more.

[WGTP]

You could use diodes to ground after the 2nd stage instead of between stages and it would be more noticable at the end.  I'm not sure the first stage will have enough level to distort much with the diodes there, especially if you use the GE's in the loop

My breadboard currently has 2 stages, but the first is non-inverting, like a Distortion Plus, Rat, etc.  The second stage is inverting, like the ones here.  This is how a Blues Breaker is set up.

I guess that makes it a cross between a Rosey Ray and a Muff Fuzz.  Muff Ray or Rosey Muff.

Anyway the non-inverting design provides more gain and is quieter, if I understand correctly.

All this is why the diodes to ground may need to go to the end.  

Finally, the Mutant Muff Fuzz I have boxed, just uses the first stage with 170K input resistor 1 Meg in the loops a 1K/.22uf (to reduce the bass some) between stages and an LED/SI clipping diode combo and it ROCKS.  Sounds good with the guitar turned down too.  

[Dragonfly]

...so my "guess" is that this will cause an "adjustable bias" for the 2nd stage ? hmm...could be pretty cool....

Exaqctly.

Some will like thiese sorts of sounds and some will not. Let your ears decide. Adjustable bias in a transistor feedback circuit will lead to instabilities that an opamp circuit will not produce, but then a mis-biased opamp will produce sounds that a mis-biased transitor won't.

of course, if i wanted to get "stupid" with it, i could simply use a dpdt switch to "choose" between the pot (variable resistor "gate") or the standard, stable voltage divider

ok...i checked the schemo on the black ice...easy enough to implement...think it'd make a fair difference to the sound?

I have such a diode pair in my Strat and I really like what it does when the pot is turned up to about 30-40%. It works like a treble control to a degree, but rather than just eliminating the treble, it replaces it with some crackle. I don't use my regular tone control any more.

sounds worth a bit of an experiment  

[Dragonfly]

You could use diodes to ground after the 2nd stage instead of between stages and it would be more noticable at the end.  I'm not sure the first stage will have enough level to distort much with the diodes there, especially if you use the GE's in the loop

seems a bit more logical...especially if its switchable or on a pot...

My breadboard currently has 2 stages, but the first is non-inverting, like a Distortion Plus, Rat, etc.  The second stage is inverting, like the ones here.  This is how a Blues Breaker is set up.

I guess that makes it a cross between a Rosey Ray and a Muff Fuzz.  Muff Ray or Rosey Muff.

my "vote" goes to the "Rosy Muff" ...then again, my vote always goes to the Rosy Muff   :shock:

Anyway the non-inverting design provides more gain and is quieter, if I understand correctly.

All this is why the diodes to ground may need to go to the end.  

Finally, the Mutant Muff Fuzz I have boxed, just uses the first stage with 170K input resistor 1 Meg in the loops a 1K/.22uf (to reduce the bass some) between stages and an LED/SI clipping diode combo and it ROCKS.  Sounds good with the guitar turned down too.  

sounds sweet....  :twisted:


btw...am i a freakin' loon for undertaking this twisted fuzz design ? (thank god for you guys' great ideas...)

[WGTP]

If we weren't LOONS, we wouldn't be here.  

This is the link I was looking for.  Check out the schematic.  

http://www.diystompboxes.com/sboxforum/viewtopic.php?p=186619&highlight=double+muff#186619

Really, the version I mentioned is plenty, unless your guitar has 000 output.   :twisted:

[Dragonfly]

If we weren't LOONS, we wouldn't be here.  

This is the link I was looking for.  Check out the schematic.  

http://www.diystompboxes.com/sboxforum/viewtopic.php?p=186619&highlight=double+muff#186619

Really, the version I mentioned is plenty, unless your guitar has 000 output.   :twisted:

mmmm....double muff ...rosy muff....  ...that diode array seems like it'd be pretty cool to experiment with!


btw...heres the next evolution schemo, which includes a pulldown resistor, a pair of switchable diodes to ground (probably something like 1n4001's), and a 10k pot wired as a resistor which "loops" the second stage, hopefully causing a bit of oscillation  :twisted:

[Dragonfly]

Since I kind of have this half way done to start with, I may as well go the whole route and see what the added op amp does for it. I believe, I'd like to keep my first section with the LEDs in the feedback section, and then have another stomp switch to engage the second stage for lead work. All I have to do now is get a wheel barrow to hold all the pots I'll have to have! This ought to be intersting Thanks for all your work on the schematic, it's cool to watch it evolve.

ain't this fun !

[Dragonfly]

aarrrgghhhh !!!  for some reason the pulldown resistor isnt showing up on the schemo, even though it clearly shows up on my photo hosting service....

 :evil:


anyway, its a simple 2.2M resistor to ground between the "input" and the .1uf cap at the beginning of the circuit.

[Dragonfly]

question for Mark, WGTP, Peter, etc....

if you took a pot (wired as a resistor) to ground between pins 2 and 6, would that act as a "gate", by throwing off the bias to the second stage of the opamp ? if so, it'd be easy to put a switch to it, and have a adjustable gate as an "option"....