2nd stompbox success! well mostly, read on...

[philbinator1]

I got my second project going!  A Fuzz Face.  Looks like hell inside...but it's going (see the theme here).      the vero diagram is below,
i also used Brian Wamplers 3PDT diagram in his diy book.

there are some issues with it i'd like to fix if i can.  the first time i tried it i got next to nothing (small gated noise if i turned the amp waaay up) so i
started fiddling...i ended up moving the ground from the dc jack (i didn't put a battery in it) to the sleeve instead of the ring, will this make a difference
to anything?  do i need the ground to go to the ring to?  the pedal switches on without any jacks plugged in, maybe this is why?

lack of volume; i'm only getting just enough vol to run on if i max out the vol knob.  is that normal?

when i turn the gain up past 3/4 i start to get a strange intermittant hissing, kind of like rain of a tin roof...?
also, nothing happens when i turn said knob from 6 to 12 oclock, just 'dirty' fuzz.

the diagram says if no bc108's use 2n3904's; i used a bc108 equivalent from Dick Smith called a BC458b, but the hFE measured from my DMM
is on average 360!  is that too high?  cos the 2n3904's are averaging 160-ish..?  should i use them?



thanks for your patience guys, slowly but surely and with your (MUCH appreciated) help i'm learning!   

[John Lyons]

When you plug in a mono plug (guitar cord) the ring and the sleeve make a connection.
This assumes a stereo input jack of course
So when you connect the ground wire (black) of the battery to the ring the input jack switches the power
on connecting the ground wire to the rest of the circuit.

You can connect the black battery wire to the ground lug of the DC jack and then to the ring as well.
This does the same thing but keeps the red and black wires close together and tidy.

So with no plug inserted in the input your power is disconnected.

I would try to find some lower gain transistors. I like 2N2222A or 2n3904.
2N3903 are nice to for lower gain sounds.

WHat is the viltage on  the collector of Q2?
It should be in the 3-6 volts area. 4.5 is typically "Good".
This is directly related to volume as well.

The noise is probably from the gain of the transistors.
Try a .01 cap from the base of Q1 to ground.
You can go smaller of course. Just touch the cap across those
two points until you find one that makes the noise go away.

john

[philbinator1]

When you plug in a mono plug (guitar cord) the ring and the sleeve make a connection.
This assumes a stereo input jack of course
So when you connect the ground wire (black) of the battery to the ring the input jack switches the power
on connecting the ground wire to the rest of the circuit.

You can connect the black battery wire to the ground lug of the DC jack and then to the ring as well.
This does the same thing but keeps the red and black wires close together and tidy.

So with no plug inserted in the input your power is disconnected.

I would try to find some lower gain transistors. I like 2N2222A or 2n3904.
2N3903 are nice to for lower gain sounds.

WHat is the viltage on  the collector of Q2?
It should be in the 3-6 volts area. 4.5 is typically "Good".
This is directly related to volume as well.

The noise is probably from the gain of the transistors.
Try a .01 cap from the base of Q1 to ground.
You can go smaller of course. Just touch the cap across those
two points until you find one that makes the noise go away.

john

ok!  i took your advice and add a .01 cap from Q1 base to circuit board ground, worked perfectly.  didn't try any other values, noise gone.

i replaced first one (got weird ocillations with gain knob on full, and/or guitar volume on zero..?) then both trannies to 2N3904's, reduced the noise
(and radio stations) and hiss even more.  i get the feeling i could have gone even lower still.

but, i still don't have a wire from input ring to dc ground; i tried and it made no diff to the led even when gat lead was unplugged?  i am using a stereo
jack, btw.  i took some readings, according to what you said they seem a little off:

Q1 - E: 0.0V
       B: 0.64V
       C: 1.44V

Q2 - E: 0.77V
       B: 1.44V  (this was around 3.2 before i changed the trannies)
       C: 2.87V

it's still very usable and sounds pretty good, i just have to have the volume all the way up to match the clean channel (is that called "Unity"?)
and for some reason the gain doesn't kick in at ALL until about 2-3 o'clock!!?   any suggestions?

thanks again!

[Quackzed]

r2 + r3 are the bias resistors and usually need a bit of tweeking to accomodate transistor variance. i'd start by cutting r2, and connecting a pot/trimmer in its place, to adjust by ear, find the sweet spot, measure the pot and replace it with that value resistor. same with r3.
also, if it's biassed ok, and is just not loud enough, changing r1 to say 1k or 2k will get you some more volume.

[philbinator1]

Thanks Gil, i didn't know about that biasing stuff..i'll go try now 

[philbinator1]

r2 + r3 are the bias resistors and usually need a bit of tweeking to accomodate transistor variance. i'd start by cutting r2, and connecting a pot/trimmer in its place, to adjust by ear, find the sweet spot, measure the pot and replace it with that value resistor. same with r3.
also, if it's biassed ok, and is just not loud enough, changing r1 to say 1k or 2k will get you some more volume.

hey thanks for your help guys!   i did that with r2 and r3...didn't notice much difference with r2 on diff. ohmages so kept that the same (33K).  R3 had big differences though.  I put a double-ganged 50KA pot on there and around 9K sounded good to me, but when i put a 9K resistor (a 8.1K and a 900R joined end to end) it sounded different, so i ended up putting a 10K trimpot in there.  wired the wrong 2 lugs in so it goes backwards; but ah well it still works anyway!  then i changed r1 to 1K and it made enough of a volume boost to give me some headroom (now it's at around 2 o'clock, not on full).  

How can you tell when it's biased properly though?  is it the place in between it sound gated/constricted and farty/too loud?  I'm guessing so?  I'm still having the 'Fuzz' knob to nothing at all until about 3 o'clock, then everything happens in a short space of knob-twist.  any remedies for that?


cheers me hearties   
phil

[Quackzed]

How can you tell when it's biased properly though?  is it the place in between it sound gated/constricted and farty/too loud?

yeah, basically. Most people seem to just use their ears. at one end it will be gated and the other end usually plunky and farty, in between
those extremes there is still a wide range of more compressed to less compressed sound. i usually try to find a spot where there is not too much difference in volume between the rolled off guitar volume pot at @7 and the full fuzz guitar volume at 10 sounds. so i tend to bias into the slightly compressed side ... but no 2 fuzzes will be identical and it's just part of their mojo that they each have a different sweet spot range...
- the fuzzyness does get bunched up toward the end of the fuzz pot, thats normal, but I never really felt the need to fix that, though i would guess that a linear pot or a reverse audio pot might give a different taper, better-worse... not really sure

[Brymus]

Hey way to go Phil.
Nice to see you getting your stuff working,and usable.
Sure makes it nice when you can play through your own gear.

[philbinator1]

How can you tell when it's biased properly though?  is it the place in between it sound gated/constricted and farty/too loud?

yeah, basically. Most people seem to just use their ears. at one end it will be gated and the other end usually plunky and farty, in between
those extremes there is still a wide range of more compressed to less compressed sound. i usually try to find a spot where there is not too much difference in volume between the rolled off guitar volume pot at @7 and the full fuzz guitar volume at 10 sounds. so i tend to bias into the slightly compressed side ... but no 2 fuzzes will be identical and it's just part of their mojo that they each have a different sweet spot range...
- the fuzzyness does get bunched up toward the end of the fuzz pot, thats normal, but I never really felt the need to fix that, though i would guess that a linear pot or a reverse audio pot might give a different taper, better-worse... not really sure

yeah i must say the strange fuzz-knob charactaristic doesn't worry me too much, im having way too much fun having it on full!  I just noticed that funny 'rain on the roof' sound is back, i think because i change the resistor which changed the volume/headroom.  so now i might have to trimpot the 33k resistor i think.  i read something on fuzzcentral.com about changing the 500k pot to 100k to give more bite, might do that too.  nice to know about the volume knob though, thanks 

[philbinator1]

Hey way to go Phil.
Nice to see you getting your stuff working,and usable.
Sure makes it nice when you can play through your own gear.

thanks for the kind words bro!     sure does feel good to get it going, it's given me confidence to try something a little harder, probably the BSIAB2.  then the Dr boogie.  then...the world!  MWAH-A-AHHH