Fuzz face to harsh at 100%

Steve77

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B3386F1B-1A77-442E-AE8F-974027581A7E.jpeg BE82E9A6-90F8-4EA5-95B4-18E3E423FCDF.jpeg Built a fuzz face a while back. It’s silicon using bc108s. I first built using components I had lying around. Worked well enough, except at the very end of the fuzz pot sweep. Right as it hits 100% it changes to a harsh hissing fuzz. This is a small problem as the fuzz sounds great up till that point. I’d be content to just live with it like this, except I can’t help feel like I’ve done something wrong somehow.
In an effort to trouble shoot, I ordered a silicon fuzz face component kit and came across fuzz face pots from someone local in town. I’ve even changed the transistors out for other bc108s bc109s and a few others with no change. I had added a trim pots in place of a few resistors to try to bias the transistors a little better. No change again. The circuit board, being very basic, I hand etched myself. I wondered if I had screwed that up somehow but I’ve gone over it and over it and all the paths are clean. Nothing accidentally connected.
I’ve never actually owned a fuzz face before. Does the fuzz really go a little crazy at the end of the sweap?
Is this an issue anyone else has had before?
sorry I only have these two pictures right now. I’ll add more when I get home. The first one as the etched board on the left. The right one was a colorsound power boost which worked perfect.
Can I add a sound clip here? I’ve never done that before. I can try a YouTube video if need be.
Thanks for any help! You folks have always been great!
 

Steve77

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Sorry I should say. I changed components and biased transistors with no change to the harsh fuzz at the end of the sweep. Of course there was the expected change from biasing and using different transistors. Just not to the harsh 100% fuzz
 

Steve77

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Hmm, I don’t think so. I’ll have to experiment when I get home to make sure, but I’m 99% sure. It does do it with all my guitars or amps. Humbuckers of various types and vintage style single coils on my Strat. But I’m pretty sure calms down the crazy fuzz when the guitar volume is rolled back.
 

Steve77

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Just read all the mods. I’m intrigued. May run through a few of those. I do like the idea of tightening up the low end and smoothing out the fuzz just a bit.
I came across the idea that this could be oscillation from high gain transistors at max on the fuzz pot. I don’t have any experience with oscillation, so I couldn’t say for sure. I’m going to compare what I’m getting to the description. Maybe that’s what it is. I’ve read just adding a resistor to the fuzz pot to keep it from maxing out is a solution. Doesn’t really seem like much of a solution though. I could just not turn the pot on full. Just as easy.
if it is oscillation, is there any other better fixes?
 

drmordo

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I know there was a classic FF that used BC108s, but IMO they are too high gain for a FF. I wonder if the 'hiss' you are hearing is really a very high freq oscillation due to the high gain transistors.

I built the Axis Face maybe ten years ago, and honestly I think it sounds at least as good as my Roger Mayer Ge Fuzz Face (I omitted the Smooth control). He recommends extremely low gain transistors, and I used the same ones he did. For a while, I experimented a bunch of other transistors, but eventually I went back to the Axis Face recommendations.

https://fuzzcentral.ssguitar.com/axisface.php
 

Steve77

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Ok so finally got home. Swapped out what turned out to be bc109b transistors for some crappy, but low gain transistors (pulled them out of an old tape deck). They sounded horrible, but the noise at max gain was gone. So fair enough, I’m using transistor that were really high gain. I had a set of bc108s that were far less gain then the 109s. Know clue why I hadn’t used those in the first place. Threw them in, did a few of those mods to smooth it out and take out a little low end. Sounds fantastic!
so... a guy walks into his doctors office and says “doctor it hurts when I do this”. The doctor looks at him and says “well then don’t do that!”
So, if the pedal sounds great except for the last tiny bit of the fuzz knob, then I just won’t turn it up that high. I guess I could add a resistor or trim pot after the fuzz pot to keep it from going to max, but meh I could just not turn it up that high.
Problem not so much solved as understood.
Thanks again!!
 

loopfinding

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I have no idea about the dark arts of RF design, but can’t there be problems of oscillation in high gain circuits where you have signal traces close to each other doubling back? Maybe it’s a routing issue? There are some things in your layout that would make me a little nervous (close parallel traces, loop-ish looking things).
 
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allesz

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I think you described the regular behaviour of a fuzz face; maybe with germanium trannies It would be different, not sure.

I always keep the fuzz pot a little bit above the three o' clock mark, at max It Is just too much and nasty.

If you really hate this behaviour, you can put a small value resistor (around 100 ohms?) In series with the fuzz's pot leg that goes to ground... Or even the One leg that goes to the electrolitic capacitor... I think It Will only depends wich way Is easier/cleaner.
 

DougM

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Does everyone just use only one version of the word "to" now, even if the correct use is "too" or "two", because I see this all the time everywhere online. It's even more ubiquitous than using "your" in place of "you're", or "should of" instead of "should've" (should have).
 

TokyoPortrait

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Does everyone just use only one version of the word "to" now, even if the correct use is "too" or "two", because I see this all the time everywhere online. It's even more ubiquitous than using "your" in place of "you're", or "should of" instead of "should've" (should have).

Sorry, which post are you referring to, or, which posts are you referring two? I couldn't tell form what you wrote.

ETSBWTYIL* :lol:

Pax/
Dean
*secret acronym
 

Steve77

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My bad, your right it should be
Fuzz face “too” harsh. I’m usually better with that.
I was actually just watching the jhs video. Good info. I’ll be giving some of it a try.
Is there a way to post a sound clip here? SoundCloud YouTube type thing?
 

pi

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I know there was a classic FF that used BC108s, but IMO they are too high gain for a FF. I wonder if the 'hiss' you are hearing is really a very high freq oscillation due to the high gain transistors.

I built the Axis Face maybe ten years ago, and honestly I think it sounds at least as good as my Roger Mayer Ge Fuzz Face (I omitted the Smooth control). He recommends extremely low gain transistors, and I used the same ones he did. For a while, I experimented a bunch of other transistors, but eventually I went back to the Axis Face recommendations.

This matches the research/articles I saw too. I built two silicon fuzz faces, and neither had this issue. I used a low gain for q1 and medium gain for q2 in both.
 

Fretting out

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Just don't turn it all the way.

I'd like to hear a sound clip. Could be usable for something.

Ha!

I was looking through here and thought I’d be the one to say it

If it hurts when you touch it? Don’t touch it

I’d like to hear it too, maybe it’s normal sounding to some of us fuzz weirdos
 




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