Fuzzface issues!

[Clint Eastwood]

To be honest, Flynn, until six months ago I didn't know what a fuzz face was. I have built exactly 1 so far,  sounds pretty good to me, with sort of standard gain transistors.  So I can't tell you what is a good or a bad fuzz, and I think in the end only your ears can.
There are folks out there saying they have super sounding fuzzes with low gain transistors.

[Flynn]

well i guess i am one of them!  so far so good anyway.  checked it out tonight with a crappy little practice amp.  tomorrow i'll crank up the tube amps and see what they have to say...

[pinkjimiphoton]

That schematic is faulty.  I think it's supposed to be the Fulltone (not sure).  But the 470k resistor up top should be 470 ohms, or something close to that.  Major difference.  The 100k on Q1e isn't right either.  100 ohms would usually work, but original FFs went straight to ground.

Edit:  Beat by Clint, but posting anyway to back him up.  (As if Clint Eastwood ever needed backup)

yeah, its an analog man sunface schematic, but its got issues. over complicated, and bad values.
5k for the gain pot is way too high. they wanna see more like 500ohms to 2 k max... 2 k doesn't sound very good, either on any of my builds. i've built around 300 variants of the fuzzface from the actual components to some wack shit i found on the net...

500k is fine for the output, and is the stock fuzzface value

10k for the sundial is fine too.  stock value biases at 8.2k (fixed resistor)

r4 should be 470 ohm. you can go to 330 ohm or so, but at 470k you're starving q2 so there's no way to get a proper bias.

input cap can be anything, but stock value is 2.2u

output cap is kinda small too unless you're looking to limit the wooliness of it.

trimmer is shown as a potentiometer/voltage divider.

it should be a variable resistance... no connection to ground. as shown, its a volume control. as a variable resistance, it acts as a "passive buffer" so you can put a wah in front of it without out of control oscillations.

looking at the voltages, did you check the pinouts of the q's? not all are ebc or cbe, i've got a couple hundred awesome sounding soviet ge npn's that are ecb pinouts.
you sure they're not reverse beta'd? hey... it happens...

[pinkjimiphoton]

higher gain q's just tend to make it harsher sounding. there's definite sweet spots for the gain.
if you think your gain is too high, try adding small resistances between e and ground on q1... 40-220r is usually a good place to start. it doesn't take much to get it in the sweet ballpark.
you can tell its right when ya can roll your guitar down and it cleans up well. ideally, barely on on the guitar volume should be cleaner sounding than when bypassed (more highs and mids)

[Flynn]

hiya pinkjimiphoton,
thanks a lot for all the info.  damn, you have built a lot of these things.

Removed the ground lead from the input trimmer.  (should this be done for the Sundial as well, as previously suggested?)

Tried out a 2.2uf on the input and i'm really not hearing any big difference, like you said.

I put a .1uf on the output instead of the .01 - huge difference in low end, way better.  thank you for that!  Sounds cool enough on bass, too now.

Gain is fine for me. 

I am hearing some whining/oscillation - wondering if that's lead dress that will be cured when soldered up.  I thought i read where putting a small cap across the base and collector (or something along those lines) would help that?

[Jolly Jimmy]

I am hearing some whining/oscillation - wondering if that's lead dress that will be cured when soldered up.  I thought i read where putting a small cap across the base and collector (or something along those lines) would help that?

Have you any power filtering in place? I wouldn't have thought you'd be getting oscillation problems with such low gain transistors, so I would suspect the power supply. Try a 100µF cap across the power rails or use a battery, see if that helps.

[Flynn]

hi Jolly Jimmy,

it's a wallwart.  i'll try with a battery to see and dig up a 100uf cap, as well.

[Flynn]

Got rid of a lot of the whining just with lead dress / wiring.  Still some nasty background noise but it is still on the breadboard.

I thought i would post a little test i did where i switch the bias resistors (2.2k on the schemo) and the output cap.


https://soundcloud.com/user-342548702/mod-tests-germface-germanium-fuzz-face-based-on-coda-schematic-of-sundial


Recorded using a strat clone into the effect then DI'd using a hybrid tube preamp (Summit 2BA-221) into the soundcard. 

The snippets are in this order:

1) No bias resistor, .01 uf output cap
2) 1.5k / .01uf
3) 2.2k / .01uf
4) 3.3k / .01uf

1) No bias resistor, .1 uf output cap
2) 1.5k / .1uf
3) 2.2k / .1uf
4) 3.3k / .1uf

I might just use some of these 4 position rotary switches i have to include all the above options.

I would love to hear what y'all think.  Does this sound like what one might reasonably expect from a FF?  Can you tell my transistors are lower gain?  Any suggestions or feedback?

Cheers

[Flynn]

i see there are no takers for giving me feedback on how it sounds!!!   

well, i also did a rangemaster and a 'muffer' (with my own clipping section design). 

here's  a recording with my Muffuzz on the left, Fuzzface on the right, and Rangemaster around center.  i slapped on a bit of compression and reverb on the master buss and here it is:

https://soundcloud.com/user-342548702/fuzz-range-muffuzz-mix-di-mastering

[antonis]

i see there are no takers for giving me feedback on how it sounds!!!   

Do you want US to give you feedback for YOUR pedal..??

[Flynn]

ha!  YES!!!    i've asked for everyone's input on everything else, why not that!   

[Flynn]

I'm back with... more Fuzzface issues!!!

So i created a stripboard layout from the schematic with my little mods in there and soldered it up.

Bypass works fine (hearing the clean guitar) but no fuzz.

Using my audio probe I am getting lovely fuzziness at the collector of the 2nd transistor. 

So, I'd guess that the problem is between there and the output jack. 

I have no mods between these two points aside from the bias/sundial pot being 20k instead of 5k.

***When I turn the Bias (Sundial) control fully counter-clockwise the pot starts to CATCH ON FIRE!   

I am using a wallwart 9v supply, by the way, which had worked fine on the breadboard.

I thought I would check with you cats now before I spend tomorrow toiling and burning out pots!

I am working from the same schematic as in my first post (except for my mods which just change out some caps and resistors). 

Here's my stripboard layout:

[Flynn]

I completely misspoke regarding there being no mods between the collector of Q2 and the output:

There is a switch to change the output cap (C3) between 2 different values.

There is a 4 position switch to change out R3 (the bias resistor) to different values - I know that this mod works fine because I can hear the changes when using the audio probe at the Q2 collector.

[Flynn]

Ok, I found a few of my screw ups:

1) trim and bias should not have their left lugs grounded (as pointed out to me earlier in this thread).  Pot not flaming now.
2) my layout shows r4 as 470k, it's 470r.

Getting some low-volume fuzz from the output now - along with a much louder whining noise.

Going to check some voltages and dig around with the audio probe next...

[Flynn]

So, i realllly should have done a schematic for this thing that includes my 'mods' a long time ago, but here it is.

The issue i'm having is pretty baffling. 

With the audio probe I get green lights all the way to the bottom of the bias pot, but nothing on the wiper.  (Fresh 20k pot).

When I bridge the connection between the bottom of the bias pot and the output pot using a fresh cap, everything seems to be fine and the bias control works.

If I try that same connection from the wiper of the bias pot, I get nothing.

I have tested for continuity and everything is checking out ok.



Any suggestions much appreciated...

[thermionix]

You say A-B continuity, can you elaborate?  You should have from 0-20K ohms, depending on the trim pot setting.  For a meter to give a continuity beep, it would need to be quite low resistance.  Did you connect A to B instead of A to wiper?

[Flynn]

Hi Thermionix,

Correct, with the pot turned fully clock-wise I see continuity from A (the 470r) to B (the right lug). 

I'm just using my meter's lowest resistance setting to check.   

Wiper goes to the 470r, left lug unattached, right lug to bias resistors.

[PRR]

> I see continuity

"Continuity" is for checking trailer lights, maybe basic poking at electronics.

But if you don't get happy fast, electronics technicians look at the OHMS numbers. There may be a real difference between 4.7r and 470r. Report those (probably with pot in several positions) and maybe someone will spot a problem.

[Flynn]

hey PRR, thanks for the post!

but!  I JUST found the issue...

there was a single wire out of the wire braid that was touching between C and D on the stripboard... i did a continuity test between each track on the board and found this one.  i usually do that check after each solderpoint, not sure why i missed this one, but there it is.

works a charm now!

Yahoo!  Thank you to all of you!