FUZZ FACE build - pots question...am i going crazy

Frequent questions about dead or faulty pedals. Whether you repair, mod or build pedals, debugging is important. Threads about general debugging problems irrespective of the circuit involved...

FUZZ FACE build - pots question...am i going crazy

Postby mojoh » 18 Sep 2009, 05:28

ive finished wiring up my fuzz face (silicon NPN)
as per this diagram
http://www.aronnelson.com/gallery/main. ... 1.gif.html

i have a question RE the Pots...

is that link correct in using a 1K Audio/Log pot?

ive checked a few other sites (GGG etc) and it seems to indicate it needs a 1K Linear ?

i wired it up with a linear pot and it sounds fine until you dime the levels...then it goes all space ship noise on me (this could be because of the BC108s...i socket them so just slapped 2 random ones in quickly and/or that i was testing the pedal not mounted in the enclosure)
mojoh
Breadboard Brother
 
Posts: 148
Joined: 25 Aug 2009, 05:43
Has thanked: 0 time
Have thanks: 0 time

Re: FUZZ FACE build - pots question...am i going crazy

Postby RnFR » 18 Sep 2009, 06:27

use whatever sounds good. to kill the oscillations, either move around the wires in your build or better yet, add a small(100-470pF)cap between B and C of Q1.
"You've converted me to Cubic thinking. Where do I sign up for the newsletter? I need to learn more about how I can break free from ONEism Death Math." - Soulsonic

Blog-APOCALYPSE AUDIO
User avatar
RnFR
Old Solderhand
 
Posts: 5138
Joined: 09 Jan 2008, 07:02
Location: Inner Earth
Has thanked: 150 times
Have thanks: 174 times

Re: FUZZ FACE build - pots question...am i going crazy

Postby mojoh » 23 Sep 2009, 04:33

i mounted the pedal in the enclosure and it seems to be better...however when you play a note...there is this crackling,fizzling undertone that rings out then just fizzles completely away while the actual note is still sustaining.
and when the 2 knobs are on full it is full on screeching and when you turn the guitar volume down...it sorta has a flanging high pitch phase effect...in a non musical way

will placing the small cap across B and C of Q1 be resolve this issue?

ive also check all my wiring and solder points.
mojoh
Breadboard Brother
 
Posts: 148
Joined: 25 Aug 2009, 05:43
Has thanked: 0 time
Have thanks: 0 time

Re: FUZZ FACE build - pots question...am i going crazy

Postby mojoh » 23 Sep 2009, 04:42

i should also add...im using the tonepad 3dpt wiring for led (two 3mm leds with a 1k resistor) and power supply
same diagram as the first post
http://www.diystompboxes.com/smfforum/i ... .msg617943
mojoh
Breadboard Brother
 
Posts: 148
Joined: 25 Aug 2009, 05:43
Has thanked: 0 time
Have thanks: 0 time

Re: FUZZ FACE build - pots question...am i going crazy

Postby dtjesus » 23 Sep 2009, 12:12

I have had the same issue with a number of fuzz faces i have built on stripboards or breadboards. I have tried both linear and log for gain control and in both cases they produce high screeching noise as soon as you hit the max end of the pot. I tried using a 100k pot (both log and lin) between Q1 base and Q2 emitter as an alternative gain control but its the same issue.
Is that an issue with cheap pots or thats just how a fuzz face behaves?
dtjesus
Breadboard Brother
 
Posts: 51
Joined: 09 Oct 2008, 12:05
Location: London UK
Has thanked: 0 time
Have thanks: 5 times

Re: FUZZ FACE build - pots question...am i going crazy

Postby RnFR » 23 Sep 2009, 12:32

for oscillation at the extreme end of the control, you can also put a small resistor (100R) between the gain pot and ground, limiting the amount of gain available. the other problem(crackling and whatnot) sounds like it could be a soldering problem. give it another good look over and make sure all your components are correct. take a razor blade and scrape between the strips, then clean it off with rubbing alcohol. if it still happens, try my other advice.
"You've converted me to Cubic thinking. Where do I sign up for the newsletter? I need to learn more about how I can break free from ONEism Death Math." - Soulsonic

Blog-APOCALYPSE AUDIO
User avatar
RnFR
Old Solderhand
 
Posts: 5138
Joined: 09 Jan 2008, 07:02
Location: Inner Earth
Has thanked: 150 times
Have thanks: 174 times

Re: FUZZ FACE build - pots question...am i going crazy

Postby mojoh » 25 Sep 2009, 05:48

RnFR wrote:to kill the oscillations, either move around the wires in your build or better yet, add a small(100-470pF)cap between B and C of Q1.


do you place the cap on the underside/solder side of the veroboard where the B and C are?
or just tack the cap to the 2 legs on the top component part of the veroboard

or it doesnt matter?
mojoh
Breadboard Brother
 
Posts: 148
Joined: 25 Aug 2009, 05:43
Has thanked: 0 time
Have thanks: 0 time

Re: FUZZ FACE build - pots question...am i going crazy

Postby RnFR » 25 Sep 2009, 05:53

mojoh wrote:
RnFR wrote:to kill the oscillations, either move around the wires in your build or better yet, add a small(100-470pF)cap between B and C of Q1.


do you place the cap on the underside/solder side of the veroboard where the B and C are?
or just tack the cap to the 2 legs on the top component part of the veroboard

or it doesnt matter?

either one would work.
"You've converted me to Cubic thinking. Where do I sign up for the newsletter? I need to learn more about how I can break free from ONEism Death Math." - Soulsonic

Blog-APOCALYPSE AUDIO
User avatar
RnFR
Old Solderhand
 
Posts: 5138
Joined: 09 Jan 2008, 07:02
Location: Inner Earth
Has thanked: 150 times
Have thanks: 174 times

Re: FUZZ FACE build - pots question...am i going crazy

Postby mojoh » 30 Sep 2009, 02:55

i added the 100pf cab across the legs and it got rid of the fizzing/crackling undertones.
thanks for that.


with the 100R between ground and the fuzz/gain pot the ossicilations/kettle whistling is still there when the pot is on max...however it goes away with a hair of a turn down... would a higher/lower value resolve this?
i only have a 330R available at home at the momment so contemplating experimenting with it...thoughts???
mojoh
Breadboard Brother
 
Posts: 148
Joined: 25 Aug 2009, 05:43
Has thanked: 0 time
Have thanks: 0 time

Re: FUZZ FACE build - pots question...am i going crazy

Postby fuzzyric » 02 Oct 2009, 18:06

strange

i had this prob once.

be sure fuzz pot is linear - you can try 2kB

I never use the same capacitor on the emmitter of Q2, try some, from 5uf to 1000uf can be good.

be sure of the connection in npn mode: the - of this cap on ground....the neg of other cap on circuit side

good luck
fuzzyric
 
Posts: 28
Joined: 01 Oct 2009, 22:14
Has thanked: 0 time
Have thanks: 0 time

Re: FUZZ FACE build - pots question...am i going crazy

Postby fuzzyric » 02 Oct 2009, 18:08

sorry...
teh + on the circuit side

I use to build pnp
fuzzyric
 
Posts: 28
Joined: 01 Oct 2009, 22:14
Has thanked: 0 time
Have thanks: 0 time

Re: FUZZ FACE build - pots question...am i going crazy

Postby DrNomis » 13 Oct 2010, 12:32

I had that issue withy my Fuzz Face pedal last night,i was using two BC549c transistors,one had a gain of about 650,the other had a gain of about 740,I pulled them out of their sockets and replaced one with a BC547b(gain of 309),and the other one with a BC549b(gain of 320),that stopped the issues,and I didn't have to install any capacitors at all... :)
Genius is not all about 99% perspiration, and 1% inspiration - sometimes the solution is staring you right in the face.-Frequencycentral.
User avatar
DrNomis
Old Solderhand
 
Posts: 6886
Joined: 16 Jul 2009, 05:56
Location: Darwin,Northern Territory Australia
Has thanked: 123 times
Have thanks: 397 times

Re: FUZZ FACE build - pots question...am i going crazy

Postby DrNomis » 13 Oct 2010, 12:38

I used an Alpha 24mm 1k Linear pot for the fuzz control,and an Alpha 24mm 500K Log pot for the volume control,all capacitors and resistors(except the Q2 collector resistor)are as per a silicon NPN fuzz face,I used a 15-turn 20k vertical mount trimpot for Q2's collector resistor,so I could easily set Q2's collector voltage to 4.5Volts.... :)
Genius is not all about 99% perspiration, and 1% inspiration - sometimes the solution is staring you right in the face.-Frequencycentral.
User avatar
DrNomis
Old Solderhand
 
Posts: 6886
Joined: 16 Jul 2009, 05:56
Location: Darwin,Northern Territory Australia
Has thanked: 123 times
Have thanks: 397 times


Return to Debugging

Who is online

Users browsing this forum: No registered users and 1 guest