tayda fuzz face squealing at high fuzz level

[natezaps]

I just finished building a silicon fuzz face with BC108s. When I turn the fuzz all the way up, it squeals like crazy. I have to back off a bit and it goes away.

Is this normal for a fuzz face or do I have a problem somewhere?

I am building the negative ground version. I have installed the electrolytic caps "backwards" for negative ground.

I am using a Cioks power supply that's outputting just over 9 V. I have also tried using a battery. I am plugging my guitar into the FF and then into my amp - no other pedals or anything.

I have biased my Q2 to 4.5 V

I am using a pcb I got from tayda.

https://www.taydakits.com/instructions/fuzz-face/pages/designators-and-components--26

I've noticed that when I put my finger across both transistors, the squeal completely goes away. On Facebook, it was suggested to me that I try putting a 47 pF cap across Q2 base and collector. I don't happen to have a 47 pF on hand but I do have a 68 pF. I used the 68 pf but it made no difference.
I also tried soldering the same capacitor to the tops of the transistor cans like a bridge. Then I tried using a jumper wire to do the same thing. It still squeals when fuzz is all the way up.

The only thing I changed from the instructions was to use a 1KC for fuzz pot instead of 1KB

[willienillie]

Have you considered lead dress?  Keep wires as short as practical, and route input and output wires as far from each other as you can manage.  Sometimes shielded in/out wires helps too, but can be a pain to deal with inside a little pedal.

[LightSoundGeometry]

when this happens to me the only fix is wiring or a whole new rebuild. make sure the power wire is not parallel with any audio wire , that is usually the culprit ..most times Ihave to rebuild or scrap the project when I get really bad whine

[natezaps]

Have you considered lead dress?  Keep wires as short as practical, and route input and output wires as far from each other as you can manage.  Sometimes shielded in/out wires helps too, but can be a pain to deal with inside a little pedal.

I feel like I did a good job at keeping the wires as short as possible while still having enough slack to work on it when I want to do mods. I've also tried moving the wires all around and separating power from audio. However, it literally made zero difference where the wires were. I still got the same amount of squeal and buzz with fuzz knob maxed. if I turn it down just a bit, the squeal goes away completely.

[natezaps]

when this happens to me the only fix is wiring or a whole new rebuild. make sure the power wire is not parallel with any audio wire , that is usually the culprit ..most times Ihave to rebuild or scrap the project when I get really bad whine

do you use a particular FF pcb and possibly a 3pdt switch pcb? if so, what do you use?

[LightSoundGeometry]

when this happens to me the only fix is wiring or a whole new rebuild. make sure the power wire is not parallel with any audio wire , that is usually the culprit ..most times Ihave to rebuild or scrap the project when I get really bad whine

do you use a particular FF pcb and possibly a 3pdt switch pcb? if so, what do you use?

no on some perf builds, mostly plexi style high gain stuff ..its been awhile since I i have the whine knock on wood

[willienillie]

I feel like I did a good job at keeping the wires as short as possible while still having enough slack to work on it when I want to do mods. I've also tried moving the wires all around and separating power from audio. However, it literally made zero difference where the wires were. I still got the same amount of squeal and buzz with fuzz knob maxed. if I turn it down just a bit, the squeal goes away completely.

Right on.  There could be some issue with the layout of the Tayda PCB, I've never used it, but maybe it's more likely related to transistor gain.  Maybe.  One of my first FF builds (germanium) had a squeal and also seemed too gainy to me, though my board layout may have been the real problem.

Did you measure your transistors?

[natezaps]

I feel like I did a good job at keeping the wires as short as possible while still having enough slack to work on it when I want to do mods. I've also tried moving the wires all around and separating power from audio. However, it literally made zero difference where the wires were. I still got the same amount of squeal and buzz with fuzz knob maxed. if I turn it down just a bit, the squeal goes away completely.

Right on.  There could be some issue with the layout of the Tayda PCB, I've never used it, but maybe it's more likely related to transistor gain.  Maybe.  One of my first FF builds (germanium) had a squeal and also seemed too gainy to me, though my board layout may have been the real problem.

Did you measure your transistors?

I have not measured the transistors. I don't have one of those transistor testers. I have it on my christmas list lol
I have tried swapping Q1 an Q2. Same results. I have some BC109s that I threw in there. Still same results.

[LightSoundGeometry]

I feel like I did a good job at keeping the wires as short as possible while still having enough slack to work on it when I want to do mods. I've also tried moving the wires all around and separating power from audio. However, it literally made zero difference where the wires were. I still got the same amount of squeal and buzz with fuzz knob maxed. if I turn it down just a bit, the squeal goes away completely.

Right on.  There could be some issue with the layout of the Tayda PCB, I've never used it, but maybe it's more likely related to transistor gain.  Maybe.  One of my first FF builds (germanium) had a squeal and also seemed too gainy to me, though my board layout may have been the real problem.

Did you measure your transistors?

I have not measured the transistors. I don't have one of those transistor testers. I have it on my christmas list lol
I have tried swapping Q1 an Q2. Same results. I have some BC109s that I threw in there. Still same results.

maybe the bc109's are around 400-500 hfe?  maybe you need some lower gain trans,like 50-200hfe ?

https://www.taydaelectronics.com/fuzz-face-guitar-effect.html

https://www.taydakits.com/instructions/fuzz-face

*Transistors       
Q1    PNP 2N3906 / NPN  2N3904, BC108 or BC109
Q2    PNP 2N3906 / NPN  2N3904, BC108 or BC109

hmmm ..i dont know ..bc109 are really high gain right ? time to go back to FF basic lol

the pictured fuzz tayda has ac128 in there

http://diy.smallbearelec.com/HowTos/FuzzFaceFAQ/FFFAQ.htm

https://buildyourownclone.com/products/ac12870-100

*TRANSISTORS

The original Fuzz Face uses germanium PNP transistors (AC128 or NKT275); You should use a low gain for Q1 (β=70-80) and a high gain for Q2 (β=110-130). Germanium transistors tend to have leakage current and a varying gain value. For the PNP silicon version, you can use 2N3906.

For NPN silicon version you can use 2N3904, BC108 or BC109. You can use sockets and try different transistor combinations. To use to the negative ground version (NPN transistors): change to NPN transistors, flip the polarity of the electrolytic capacitors (C1, C2 and C4) and connect the +9V where it is marked -9V.

[natezaps]

I feel like I did a good job at keeping the wires as short as possible while still having enough slack to work on it when I want to do mods. I've also tried moving the wires all around and separating power from audio. However, it literally made zero difference where the wires were. I still got the same amount of squeal and buzz with fuzz knob maxed. if I turn it down just a bit, the squeal goes away completely.

Right on.  There could be some issue with the layout of the Tayda PCB, I've never used it, but maybe it's more likely related to transistor gain.  Maybe.  One of my first FF builds (germanium) had a squeal and also seemed too gainy to me, though my board layout may have been the real problem.

Did you measure your transistors?

I have not measured the transistors. I don't have one of those transistor testers. I have it on my christmas list lol
I have tried swapping Q1 an Q2. Same results. I have some BC109s that I threw in there. Still same results.

maybe the bc109's are around 400-500 hfe?  maybe you need some lower gain trans,like 50-200hfe ?

https://www.taydaelectronics.com/fuzz-face-guitar-effect.html

https://www.taydakits.com/instructions/fuzz-face

*Transistors       
Q1    PNP 2N3906 / NPN  2N3904, BC108 or BC109
Q2    PNP 2N3906 / NPN  2N3904, BC108 or BC109

hmmm ..i dont know ..bc109 are really high gain right ? time to go back to FF basic lol

the pictured fuzz tayda has ac128 in there

http://diy.smallbearelec.com/HowTos/FuzzFaceFAQ/FFFAQ.htm

https://buildyourownclone.com/products/ac12870-100

*TRANSISTORS

The original Fuzz Face uses germanium PNP transistors (AC128 or NKT275); You should use a low gain for Q1 (β=70-80) and a high gain for Q2 (β=110-130). Germanium transistors tend to have leakage current and a varying gain value. For the PNP silicon version, you can use 2N3906.

For NPN silicon version you can use 2N3904, BC108 or BC109. You can use sockets and try different transistor combinations. To use to the negative ground version (NPN transistors): change to NPN transistors, flip the polarity of the electrolytic capacitors (C1, C2 and C4) and connect the +9V where it is marked -9V.

like i mentioned in my original post, i have reversed the electrolytic caps so i can run negative ground. that's not the issue. the pedal works except when fuzz knob is at max. if i back it down a smidge, the noise goes away and it sounds great.

also, like i mentioned before, i have no way to test transistors. i have no idea which one has less gain to use for Q1. i have 2 BC108s, 2 BC109s, and 2 2N3904s. i have not tried the 2N3904 yet. I installed sockets so i can swap them out.

I have been following all the links you posted already. as a matter of fact, i've just about memorized everything from tayda.

[11-90-an]

why dont you just try all your transistors out? 

if you did and each of them has a problem, you probably need to add a small value resistor (100 ohms can be fine) then tack it in between pin 3 of your pot and the area where R1 and Q2 Emitter are connected. (Note that there is a trace there so you would have to cut it i guess..) It basically limits the how much resistance from C2 to Q2 to at least 100 ohms. Without it, there would be 0 ohms, and squealing can happen.

[natezaps]

why dont you just try all your transistors out? 

if you did and each of them has a problem, you probably need to add a small value resistor (100 ohms can be fine) then tack it in between pin 3 of your pot and the area where R1 and Q2 Emitter are connected. (Note that there is a trace there so you would have to cut it i guess..) It basically limits the how much resistance from C2 to Q2 to at least 100 ohms. Without it, there would be 0 ohms, and squealing can happen.

I tried the BC109s. They didn't eliminate the squeal.
I will look into your solution. I hate having to break a trace though.

[11-90-an]

Not only the bc109s... try others too... like your 2n3904s.

Are you soldering the pots directly to the board? if you aren't you just have to cut the a part of the wire, and solder the resistor in. Maybe that's better than cutting a trace.

[natezaps]

Not only the bc109s... try others too... like your 2n3904s.

Are you soldering the pots directly to the board? if you aren't you just have to cut the a part of the wire, and solder the resistor in. Maybe that's better than cutting a trace.

i installed sockets fom the transistors to make it easy to experiment. i'll try out the other transistors tomorrow. my family is sleeping lol

[LightSoundGeometry]

Not only the bc109s... try others too... like your 2n3904s.

Are you soldering the pots directly to the board? if you aren't you just have to cut the a part of the wire, and solder the resistor in. Maybe that's better than cutting a trace.

i installed sockets fom the transistors to make it easy to experiment. i'll try out the other transistors tomorrow. my family is sleeping lol

yeah I was not thinking SI lol .. once a pedal gets whine it kind of always has whine, thats why I scrapped them and moved onto another build...sort of like a stiff guitar. it will always fell sort of stiff and un slinky like even wit a set up ..

[antonis]

it was suggested to me that I try putting a 47 pF cap across Q2 base and collector.

Try 150pF on BOTH Q1 & Q2..
In case of high gain setting squeal elimination, lower caps values till squeal appearance theshold..

[natezaps]

it was suggested to me that I try putting a 47 pF cap across Q2 base and collector.

Try 150pF on BOTH Q1 & Q2..
In case of high gain setting squeal elimination, lower caps values till squeal appearance theshold..

just to clarify... do you mean across the base and collector of each one or do you mean to put the cap across the cans (like a bridge)

[11-90-an]

Across base and collector of each transistor...

[natezaps]

I was able to figure out how to get this working. Hopefully this will be helpful for anybody finding this in the future. What I have determined is that Q1 needs to be a lower hfe than Q2. For Q1, look for a part number with an A at the end for example BC108A. The A means it has a lower value. use a B or maybe even a C for Q2. what ended up sounding good for me was a 2N2369A for Q1 and a 2N2369 for Q2 (there is no letter at the end of the transistor I used for Q2. I don't know if it's safe to assume it's a B).

I was not able to find any BC107, BC108, or BC109 transistors locally. So, I just bought several equivalents and mixed and matched until I found a combination that I liked.