Muff Fuzz (Adv'd DIY Effect Pedal)

[oldrocker]

I recently received the IndyGuitarist Advanced DIY Effect Pedal Book.  It showed an opamp Muff Fuzz circuit with a variable 470k resistor across the input and output of the first opamp.  I had a terrible fizzle when the notes would fade out on mine and I thought I would try and see if lowering the resistance here would help.  I didn't use a pot but I think I'll evenually add one.  I ended up using a 220K here and sure enough it almost eliminated it.  The variable resistor the the Indyguitarit book was the first time I saw that used.

[oldrocker]

I had read that to resolve this situation was to put a resistor across the diodes (470K) and that the fizzle is a normal characteristic of the opamp Muff Fuzz.  I'm not sure why a gated fizzle would be desirable in an effect but to each his own I guess.  I was thinking if pots were added at both these two points it would give the MF a more adjustable fuzz.  Anyone try this?

[WGTP]

The size of the input resistor determines gain and input impedance which effects the low roll off with the input cap and the highs.  Using a low value 10K, produces a really midrangey Rockman sort of sound.  Check out the Mockman at ROG.  100K is std. on the original, and I like 220K as well.   The 220K lowers the gain, but gives it more of an amp like distortion, rather than a fuzz.  Might raise the first feedback loop resistor to 1M to recover some gain if needed.  I think the original gates as a noise reduction technique.  Gus Smalley had several mods posted that were pretty cool including these mentiioned.  Try some LED/SI/GE combos for more variations.  The LED's sound nice and reduce the noise coming thru.   

[roseblood11]

Gus Smalley had several mods posted that were pretty cool including these mentiioned.

Does anybody know that link? Or anything about those mods?

I really wanna get rid of the sputtery decay...

Immo

[CynicalMan]

Gus Smalley had several mods posted that were pretty cool including these mentiioned.

Does anybody know that link? Or anything about those mods?

I really wanna get rid of the sputtery decay...

Immo

http://www.generalguitargadgets.com/diagrams/gus_muff_mod1.gif
http://www.generalguitargadgets.com/diagrams/gus_muff_mod2.jpg

[roseblood11]

Thanx!

The next step is to understand, which mod will solve that problem.
I think it´s the different IC and the changes in the voltage divider?

[gigimarga]

I have an old question about Muff Fuzz: is there a resistor/pot of 1M in the feedback loop of the second opamp or not (only diodes) ?
Some schematics say yes, another ones say no

[ode2no1]

i built a muff fuzz earlier this year and wanted to pull my hair out because i couldnt get rid of that crackly gated decay. i just scrapped it and built a rangemaster into that one knob enclosure.

[WGTP]

IIRC the original didn't not have a resistor across the diodes in the second op amp.  470k or 1M work well to make this into a more usable distortion.  Here are some mods I did mostly based on Gus' mods.  

http://www.aronnelson.com/gallery/main.php/v/WGTP/AlteredMuff.jpg.html?g2_imageViewsIndex=1

[gigimarga]

IIRC the original didn't not have a resistor across the diodes in the second op amp.  470k or 1M work well to make this into a more usable distortion.  Here are some mods I did mostly based on Gus' mods.  

http://www.aronnelson.com/gallery/main.php/v/WGTP/AlteredMuff.jpg.html?g2_imageViewsIndex=1

Thx a lot WGTP!
I've built mine following a schematic of analogguru, which traced it after an unit from 1977, and which had a 470K resistor across the didodes (and values of another parts are a little different).