Problems with Fuzz Face BC108

[khm9]

Thank you, I'll use 8.2k if I even decide to house this thing.

As for the fuzzface itself, it sounds unfinished. The tone is very unpredictable, like the fuzz doesn't sustain all the way, or when i turn it up I can hear tone oscillating (not much but present), unlike big muff, where the tone is much more constant and more compressed.

Or perhaps it's just the nature of fuzz face?

[smallbearelec]

As for the fuzzface itself, it sounds unfinished. The tone is very unpredictable, like the fuzz doesn't sustain all the way, or when i turn it up I can hear tone oscillating

I say again: It's not ready to box in its present state. The FF circuit is perfectly capable of giving beautiful, sustained, clean fuzz. However, it almost always needs to be tweaked for best performance. Time to buy a breadboard...

[khm9]

So to finish FF I will need to:

• solder a small cap to Q2 BC legs in order to lower down the oscillation,
• replace Q1 bc108 with a lower gain transistor,
• replace 8.2K resistor with a 10K trimpot,
• ---maybe replace 33K with a 50K trimpot in order to customize it well,
• replace normal gain pot with a reverse-audio taper if found

Is this correct? I'd like overall darker sound from this fuzzface, since mine is quite thin sounding.
 

[smallbearelec]

The list is OK. However, I say again that I would do all of the tweaking on the breadboard first. That way you are not soldering and unsoldering to get to where you want to be.

[LightSoundGeometry]

The list is OK. However, I say again that I would do all of the tweaking on the breadboard first. That way you are not soldering and unsoldering to get to where you want to be.

steve , what builds can I do with those hitachis that are in the 30-35 hfe range ? I am going to mess around with them tonight and see what I can come up with. I wanted to get some ideas from you guys though as well .

[khm9]

The list is OK. However, I say again that I would do all of the tweaking on the breadboard first. That way you are not soldering and unsoldering to get to where you want to be.

Thanks bear,
I have suffered a lot during this build: heat the soldering iron, suction, swap parts ->repeat. Complete mess. next build will first be on a breadboard first, however how are bigger schematics supposed to fit the breadboard, like some huge delay pedal circuit?

I don't think I will tweak FF on a breadboard now, since I don't have one, and would have to order it, since it would take some time, I will struggle like this for a little longer.
I'm pretty much done with fuzz face anyway, few more tweaks and I hope I'm done.

Could you recommend me some of the low gain transistors that would pair good with BC108b and give better sound overall?
Do I need to put bigger caps for darker sound or tweaking trimpots will do the thing?

And will these changes improve the problems, like oscillations?

[smallbearelec]

steve , what builds can I do with those hitachis that are in the 30-35 hfe range ?

I'm sure you have a few low-gain, low-leakage NPN devices--can be either silicon or germanium--among your spares. Refer to figure 27 in this article:

http://diy.smallbearelec.com/HowTos/BreadboardGeDarlingtonRMs/BreadboardGeDarlingtonRMs.htm

and figure 6 here:

http://diy.smallbearelec.com/HowTos/BreadboardGeDarlingtonFFs/BreadboardGeDarlingtonFFs.htm

If you want/need low-gain germanium at reasonable prices:

http://smallbear-electronics.mybigcommerce.com/low-gain-and-high-gain-1/

[smallbearelec]

how are bigger schematics supposed to fit the breadboard, like some huge delay pedal circuit?

If you can't afford one large breadboard (they come in many sizes), the small blocks like the one I show can be snapped together to create a larger array. Ideazz here:

http://diy.smallbearelec.com/HowTos/IdeaBoxAndBoard/IdeaBox.htm

Could you recommend me some of the low gain transistors that would pair good with BC108b

2N4123, 2N4401, 2N2369, 2N3440, many others if you search this board on "silicon fuzz face."

Do I need to put bigger caps for darker sound or tweaking trimpots will do the thing? And will these changes improve the problems, like oscillations?

First, find a device that works well for Q1. Get the bias right and see how you like the tone. If the devices are not too "hot" you should not have a problem with oscillation. If necessary add a C to B cap. This will suppress some high end, and maybe that's what you want. Try a larger output capacitor. When you have a breadboard, try adding a tone stack--that's really the ticket for seriously modifying the palette, but it's a more complex board.

[LightSoundGeometry]

steve , what builds can I do with those hitachis that are in the 30-35 hfe range ?

I'm sure you have a few low-gain, low-leakage NPN devices--can be either silicon or germanium--among your spares. Refer to figure 27 in this article:

http://diy.smallbearelec.com/HowTos/BreadboardGeDarlingtonRMs/BreadboardGeDarlingtonRMs.htm

and figure 6 here:

http://diy.smallbearelec.com/HowTos/BreadboardGeDarlingtonFFs/BreadboardGeDarlingtonFFs.htm

If you want/need low-gain germanium at reasonable prices:

http://smallbear-electronics.mybigcommerce.com/low-gain-and-high-gain-1/

cool. thanks sb

[brianq]

As smallbear suggested,get a breadboard, it's very essential for what we do, it takes all guess work out & puts it into reality. I believe he says they're cheaper than 5 bear skins, lol
Maybe try breadboarding a "Bazzfuss" or "Electra" for practice? Have you heard of the fuzz face calculator? It's also an awesome tool. Lots of luck in your fuzz journeys.

[khm9]

As smallbear suggested,get a breadboard, it's very essential for what we do, it takes all guess work out & puts it into reality. I believe he says they're cheaper than 5 bear skins, lol
Maybe try breadboarding a "Bazzfuss" or "Electra" for practice? Have you heard of the fuzz face calculator? It's also an awesome tool. Lots of luck in your fuzz journeys.

To be honest, I am not looking forward to learning breadboarding, I've finish one project "successfully" with some minor pain.

Fuzz Face is a simple circuit. Breadboarding a FF is quite easy, but what I am scared of is breadboarding a complex pedal, for example delay pedal that has dozens of IC's, resistors, caps, etc. If I was to make a circuit out of a schematic, yes I'd use breadboard, but if there's a vero layout that is proven to work, why bother with breadboarding it, unless you're interested in modding it right?

I guess sooner or later I'll have to face my biggest fear, breadboard.

Anyway tell me more about that fuzz face calculator please, what does it do how to use it?

[Gargaman]

Man, breadboard was the light for me.
I shot one fuzz 'in the dark', it worked. The second don't.
I realize I couldn't move on without one.

[LightSoundGeometry]

if you look at my transaction log from SB, my very first purchase was a breadboard and some desoldering tools lol

i have 6 of them now and its still not enough ..I could use about ten more and an Oscope ..if someone would buy two pedals off of me I could afford a 150 dollar Scope ..anyone selling a used O scope?

[brianq]

Here it is, pretty self explanatory,it does the math for you so you can get the correct bias.
You just need a multimeter with a transistor hfe function. There's some good info there as well.
http://www.diystompboxes.com/analogalchemy/emh/emh.html
Also a good read frm R.G. @ geofex is "technology of the fuzz face" good stuff!

[khm9]

Man, breadboard was the light for me.
I shot one fuzz 'in the dark', it worked. The second don't.
I realize I couldn't move on without one.

I'll shoot this one in the dark, since I don't any breadboards... Will get one though, after I finish this FF 

[khm9]

Okay guys, I got the trimpots, for bias, can someone explain how to wire them, I see these 3 lugs, which two to use? does it matter?

[Electric Warrior]

Here it is, pretty self explanatory,it does the math for you so you can get the correct bias.
You just need a multimeter with a transistor hfe function. There's some good info there as well.
http://www.diystompboxes.com/analogalchemy/emh/emh.html
Also a good read frm R.G. @ geofex is "technology of the fuzz face" good stuff!

I like this one better: http://www.muzique.com/lab/fuzz_face.php
Seems to be rather accurate. Pretty useful to see what makes a difference and what doesn't.

For a silicon Fuzz Face, as there is no leakage and vbe seems to be rather consistent, Q1's hfe seems to be the only variable that has a large influence on the voltages.

[Gargaman]

I believe this one is another must reading consensus here.
http://www.geofex.com/article_folders/potsecrets/potscret.htm
In this case you want your trimpot acting as a variable resistor.
This trimpot has three terminals, just like pots, let's say 1, 2 and 3.
Between 1 and 3 there's a fixed resistence that is equal the value marked on the trim.
If it's a 10k trim, there's 10k between 1 and 3.
The lug 2 moves around this range, between 1 and 3.
When the trim is turned all the way counterclockwise, the lug 2 'reach' lug 1; lug 3 is 10k far from them.
When you rotate clockwise, lug 2 moves toward lug 3, untill it reaches it; lug 1 is 10k far from them.
In the fuzz, you may connect Q2 collector to 1 or 3 (doesn't matter for you, I guess), and connect lug 2 to C3/R3.
I just build one fuzz face with a pot as the bias control. I left the unused lug (1 or 3) disconected. In my case there was a little noise wich seems to reduce when I touched it, I resolved soldering the back of the pot to ground level.
I also put a small resistor in series with the trimpot, so that there is a little, instead of zero, resistance (when the pot is full counterclockwise, if you use lug 1 and 2) between Q2 and R3/C3.

[khm9]

Thank you, I'll get on to soldering 

[Gargaman]

So to finish FF I will need to:

• solder a small cap to Q2 BC legs in order to lower down the oscillation,
• replace Q1 bc108 with a lower gain transistor,
• replace 8.2K resistor with a 10K trimpot,
• ---maybe replace 33K with a 50K trimpot in order to customize it well,
• replace normal gain pot with a reverse-audio taper if found

Is this correct? I'd like overall darker sound from this fuzzface, since mine is quite thin sounding.

This is all about tweaking!
Would you preffer solder and desolder over and over again, untill you get satisfied? or use a breadboard to do that and, once you're good, solder a once?

Follow Paul's words
"Learn Ohms Law and use it relentlessly."
and all Bear's and the other guys has said. They rock.
And enjoy your ride on the curve..