dragonfly's silicon fuzz face.... moddable?

[Fuzzy-Train]

I wanted to try and build a simple fuzz with some stripboard, since I already tried a build with a PCB, I want to try something a little harder for prep work, and soldering now.

This is the one I will be trying out.

http://aronnelson.com/gallery/album17/SILICON_FUZZ_FACE

I just have a few questions.

Can a bias control pot be added to this thing? If so, can one of you kind fellow forum members do the modifications to the layout for me. (if it's not too much trouble)

Would I be able to switch to some germanium transistors later on down the road with this pedal if I choose to do so?

What tool(s) do you guys use to cut the copper trace where it needs to be cut? Would a really sharp, thick needle work? I ask because I got it with a big set of exacto knives, handles, and whatnot, and the needles fit into a handle and are really, really sharp and strong.

Is the last strip (the one with the 2 green wires from the pots and jacks connected to it) of the board ground? I won't be using a 3 slug jack (using 2, two slug jacks) would I be able to ground the DC jack to the last strip with the green wires? If not, where would I be able to ground the DC jack? (excluding the input/output jacks, and my case because it's plastic)

Thanks for the help in advance.

[dominatrix_volleyball]

Hopefully someone smarter than me will come in here, but I THINK the following is correct.

--For a bias pot, you can replace the 8.2K resistor with a 10K pot if you just want to bias Q2 closer to 4.5V...
--You can totally drop in geraniums, as the circuit is pretty identical to a stock geranium version.
--The green wires are ground. I think you can solder the negative DC lead to the same slug as the ground, with the inconvenience of having to unplug the battery when not in use. I could be wrong about that, but I **think** that's how it goes.

Also, you might want to look up some general Fuzz Face builds.
Like the Axis Face here: http://fuzzcentral.ssguitar.com/ could be a useful read.
If you check out the Antiquity: http://www.diystompboxes.com/analogalchemy/sch/antiquity.html you'll notice they have a 1M resistor in common. Along with lower input cap values, and a 100K volume pot. Plus, check out that diode at the input... interesting stuff.
And, of course, there's this awesome R.G. article: http://www.geofex.com/Article_Folders/fuzzface/fffram.htm

Anyway.
Short answer: The Fuzz Face is a really moddable circuit. You can find mods / variants / stuff written about it all over the place.

[tcobretti]

You might want to use a higher value trimpot, 50k is pretty common.  Another idea is to build my socket face, which is designed so every component can be socketed, or build the runoffgroove multiface, which allows for much experimentation.

I use a small flathead screwdriver to cut the traces on my veroboard.

[petemoore]

  10k trimpot + 4k7 or so stop resistor worked out pretty well, a 4k7 - 14k7 range with most of the rotation usable makes fine tuning easy.

[Dragonfly]

Hopefully someone smarter than me will come in here, but I THINK the following is correct.

--For a bias pot, you can replace the 8.2K resistor with a 10K pot if you just want to bias Q2 closer to 4.5V...

i typically would recommend a 20k pot, but 10k should be just fine.

--You can totally drop in geraniums, as the circuit is pretty identical to a stock geranium version.

as long as the germaniums are NPN and of the proper hfe...this is anothe reason to use a 20k trim pot, as it helps dial in q2 a bit better if your germ is being "finicky"
[/quote]


also...regarding "cutting the copper traces...a small 4-5mm drill bit works great...insert into the proper hole, twist by hand, and it will ream it right out....(wait, that sounded really dirty !)....well, you get the idea

[Fuzzy-Train]

Sweet. Thanks a lot for the help everyone.

Would I be able to use a 20k linear pot instead of a trimpot? Is it better to use a trimpot?

[tcobretti]

If by linear pot you mean a normal pot you mount on the case, sure, it'll work. 

[Fuzzy-Train]

Yeah, that's what I mean. That's good news man, thanks for the help.

[petemoore]

  The circuit IS a mod, I think Dfly has more than one FF thing in his stash.
  There are FF types stashed all over the place.
  They are fun to mess with! Great all round player too...
  GEO Technology of the FF...pass the thick parts of the article until you have more time, say on the 3rd readthrough...
  Tim Escebedo did tons of FF variants, Homewrecker?
  ROG multi-face.
  20k pot works fine, 10k does too with the stop R...like when that's whatcha got...or if you got 50ktrimpot...use a 47k parallel to it.

[Fuzzy-Train]

Didn't want to start another thread, so I'm bumping this one.

I looked around to find a different layout to follow (needed a different shape for my enclosure) and this one is exactly the same, but it's helps everything in my enclosure fit the way I want.

I just wanted to make sure that this layout is correct. It seems fine to me, but I wanted to make sure it is, and get more experienced DIY-ers to correct me if I made a mistake somewhere.



It's one of the silicon designs from Dragonfly, but I modified it only slightly with the .01uf cap. There's a trace cut under the R4 you just can't see it cause it's covered.

Thanks for your time, and help. 

[Barcode80]

polarity of C1 is backwards. input needs to be on the negative side i think, but someone else chime in and confirm.

[Fuzzy-Train]

Sorry I should have posted a link to original design. I'm pretty sure I have it the same as the original.... I think.

http://aronnelson.com/gallery/album17/SILICON_FF_VERO

How can you tell which one is positive and negative on those caps in my layout... I don't see it.

[Barcode80]

nope, you'll notice if you look closely at yours that the input cap negative side (shaded area) is facing away from the input. in the layout you are modifying, and in most circuits using an electrolytic as the input cap, the negative should face the input side, as electrons can only flow in one direction. having this cap the orientation you have it would render basically no sound, or very little.

[Fuzzy-Train]

Ahhhh, yes, I see it. It's just a little darker on the negative end.

OK, but if I solder it in like in Dragonfly's layout (positive facing down instead of up) everything else should be fine though, right?

[Fuzzy-Train]

^ Anybody?

I'd like to get this project started tonight, don't mean to be a jerk or anything, I'm just excited about it.

[Dragonfly]

i'm assuming theres a trace cut under R4 ?

a couple of things / suggestions...for higher output / more mids, change R1 to anywhere from 470R-1k

i like a 6K8 for R3, but thats just personal preference

[Fuzzy-Train]

Yup, trace cut under R4.

Always good to hear some suggestions, especially if it's from someone with as much experience as you. I think I'll just socket those resistors to make it easier to switch 'em out.

So is everything gravy?

[Dragonfly]

looks good !

have fun !

make sure you socket the transistors, so you can try different ones out !

AC

[petemoore]

  Looking at a/7 or d/3, those reds dot in red squares all mean cut that trace wire...
 c/10 and d/10 get a cut also.

[Fuzzy-Train]

Well, I finished it yesterday evening.

I had one little problem. I soldered one wire on the board in the wrong place... easy fix though.

It sounds good, but I'm getting way too much bass... sounds a little too farty for me, and I'm getting some squealing, humming etc... when the fuzz is set all the way up. I'm I right to assume it's most likely a biasing issue? I can't messure the voltage since I don't have a multimeter yet so I'm not 100% that it's the bias. I really need to get one.

I just want to make sure I'm understanding this whole biasing subject:

The voltage at the collector of the first transistor should be -0.5V, and it's adjusted by the 33k resistor right?
And the collector of the second transistor should be set to -4.5V  to -5V ( i hear 4.5 is the magic number though) and that's adjusted byt the 8.2k resistor right?

Would it be wise to remove both of those resistors and replace them with trimpots or regular (adjustable by hand) pots? I don't really want to use trimpots because my layout is extrememly small, and I don't see any way of installing one without re-doing my entire board.

In previous posts above I had suggestions to use either a 10k, 20k, or even 50k pot for the 8.2k resistor, which ones have you guys found the best to use? Same question for the 33k resistor, which pot?

Anyone ever try these mods?? :

http://www.geofex.com/Article_Folders/fuzzface/fffram.htm

Just click on mods and magic on the table of contents

BTW Drangonfly, great suggestion to use a small drill bit to cut the traces. I did one by hand, than I remembered your suggestion, and only took a few seconds for the next ones. I even drilled holes through the board around my layout so I could easily cut the board out with my dremel. Wicked advice man, made it soo much easier.

Here's a pic of the guts:


LOL the board is soooo tiny... it's smaller than a $.25
It looks diferent now though. The DC jack was replaced with a battery jack cause it didn't work, and I went back and fixed any joints that looked suspicious to me, and I cleaned up the leftover burnt rosin. This case is only temporary until I find a more suitable, bigger, metal case for it cause right now the battery, and jack are too big for it, and are outside the box.

Thanks a lot for the help everyone.

EDIT: the green wire going from the switch to the 1st caps positive was the wire I messed up, should have been 1 hole up.