Q about fuzz to clean gracefulness of fuzz face

[kvb]

I've been breadboarding PNP, NPN, germ, and Si piggybacks (2n2222, 2n4401); I even tried a double piggyback (two trans stacked + a piggybacked with 3K3R), and I've stacked a Si plus the Germ.

Everything seems to sound fine.
voltages are what others report as normal.

I think I know what the fuzz face sound is (notes played in the middle of the neck with bends sound special)

So I'm wondering, as the note decays and the fuzz sound starts to fade, it goes all the way to clean - which is what is supposed to happen . . .
but I hear a crackling even with the gain set lower and with input attenuation. There is no gating nor lack of sustain.

If it was a Jfet it would sound like mis-bias.

It is not a terrible crackle, Its just a bit annoying, like a little zzzzzzzziiiiipp at the end of notes that are held for a long time.

Is a fuzz face supposed to be more graceful or does this sound like a normal fuzz face note fade?

[GibsonGM]

Sounds normal to me, ha ha!  You'd have to go back to 60's tunes like "Incense & Peppermints" and give a listen. FF's have a cut-off point where the 1st transistor can't turn on the 2nd below a threshold...sometimes it's choppy like you describe.  Some are more smooth than others, of course.  For a really creamy, long-sustained fuzzy distortion, check out the Big Muff Pi.
Search here for FF mods, and you might find some trimpot ideas that will give you more tweakability, though....I bet you could dial it in a little closer to what you want.

[kvb]

Thanks for the reassurance, hee,hee

I ask because RG talks about touch sensitivity and J Gagan mentions that a properly set up FF can be cleaned up by dialing back the guitar vol.
I'm not necessarily noticing these aspects of the circuit.

So far, it seems like a double jfet circuit does a better job of the clean to gritty grind as one plays - not plays with knobs.

Trimpots?! I've tried trims on everything! + Gagan Easy, and Mayer mods.
For the high gain rip, I like the Mayer set up.

Also, for a clean to crunchy sound the best I've gotten is with an AC128 Q1 into J Orman's 2n404A with 2k emitter for higher gain.
This sounds good but as things clean up there remains the annoying buzz - which is more pronounced because it comes in right at the point when things sound perfectly clean.

I guess I need to do a bit more sound clip research . . .

PS as far as high gain, long sustain goes - I've got a double Bazz Fuss (which I now know has some similarity to a BMP) that I am trying to finish before I present it.

[bkanber]

Personally, I don't think that's normal. I just built another fuzz face and had the same problem. After a few hours of debugging, I switched out the gain pot and the crackling went away.... must've been bad.

So before you resign yourself to living with that crackle, try switching out the pot

Burak

[kvb]

Huh, I've tried both pots and 1K resistor. I even put some resistance on the ground of the cap to tame some gain - same sound.

Maybe it has something to do with the breadboard - I do have a ground plane.
Maybe I should solder one up and see if it sounds better.

[tcobretti]

It sounds misbiased to me.  You might try putting trimpots in to allow you to tune the biasing to your ear instead of to a prescribed voltage. 

[squidsquad]

My $0.02 (& I'm opinionated & kooky).  I've built many...and no matter what I tweaked to make em cleaner...I always heard something I didn't like.  A *smearing*, laying on top of the note, hard to describe, obscuring the tone.  I gave up...hate em.  Other fuzzes don't *rub me the wrong way*.  Anyway...just wonderin if maybe your hearin what I hear...a very subjective thing.  Maybe cause I never bothered to buy a set of tested germaniums or somethin...I dunno.

[hellwood]

if it wont clean up when you roll off the guitar's volume, its probable your transistors have too much gain. as for the crackle, that isnt something im familiar with ( except for the exact same problem im currently having w/ dragonfly's swirly fuzz). ill let you know what it is if i ever figure it out.

[joegagan]

a treble bleed cap on your guitar does wonders for the cleanup aspect. refer to my diagram on how i wire an adjustable treble bleed control, being able to set it to taste on the fly is an amazing thing.....


the treble content going up as the vol goes down counters that large input cap of the FF and makes it sparkle.

also, the less overall gain (stock FF specs with medium gain trannies), the less of the 'fizz' artifact you guys are referring to , in my experience. as the gain goes up, the fizz does also. the wives tale about 4.5 v on q2 collector is true, you need that for the best clean when you turn down.

[joegagan]

ps.
single coils good, humbuckers bad




ha ha ha ha ha

[Michael Weidenauer]

Joe is right, you need lots of treble for the clean sound. With the guitar volume down I have to turn up the tone-control to get a clean sound; if I turn it down the sound gets dirtier again.
Good single-coils and a no-load tone pot (you can DIY these pots easy - no need to buy the expensive Fender part) should work fine (I don't like the treble bleed cap across the volume pot).

[Gus]

Some of the "clean" is due to the value of the feedback resistor.  I would guess you are using a 100K.

[kvb]

Well, I'm pretty sure that what I am hearing as the note trails off is the last bit of asymmetrical clipping.
I am also pretty sure that what I'm hearing has more to do with the transistors than anything else.

The smoothest transition I'm getting with the NPNs  is with  (Aron's germs - I think there the same as what smlbr sells)
Q1 = CV7003 stacked with a 2n4401 with a germanium diode + 3K3 pig style; Q2 is CV7003 stacked with a 2n2222.
But, I tuned the 10K trim by ear to something higher than 4.5V. So as the note fades the crackle/ last bit of fizz deminishes smoothly. But I'm not sure that this is a true Fuzz face sound

Gus, I also have changed the feedback resistor to 47K, as you recommend, and I was confused by the fact that there was not much change in the type of crackling I was hearing.

The thing that is most interesting about the circuit is how one small change in a component value changes the voltages and sounds so much. It is easy to see why someone could get hooked on building fuzzes with a variety of characteristics and different types of transistors. 

With the hours I've been working I'm only able to poke around for about a half hour on weeknights.
I think tonight I'll try to set up an hfe checker so I can start doing some math and report more meaningful data.

[R.G.]

I don't know the particulars of what is really happening for you.

But I do know that high gain circuits are prone to parametric oscillations - that is, they oscillate on only part of the waveform, and it never gets to be huge. Many solid state power amps exhibit what is known in the amp biz as the "bottom side fuzzies", describing the RF oscillations that ride on the negative going side of the output as a result of PNP devices being different from NPN devices. Sometimes it is only big enough to look like a thickening of the scope trace, and sometimes it takes a multi-hundred-MHz scope to see it AT ALL because the frequency is so high. It can be very difficult to see, let along prove. But it would cause symtoms like you describe.

Since it's happening with all varieties of transistors for you, if it were me I'd clean up the power supply decoupling, grounding and layout. Might help.

[joegagan]

interesting, rg

i think there is some background fizz in a lot of signals, but people aren't really listening for it.

but once you notice it, you turn into a sleuth for fizz and artifacts.

example , your amp sounds fine on the gig but when you are preparing to record ( or worse, get into the studio with the clock ticking before noticing) your cabinet is rattling and buzzing on certain notes that the mic is picking up. time to tighten up the cab.

one time during a sound check my brother noticed that he was getting mic feedback if he held his mouth open a certain way and stood a little up and to the right. he spent about 5 minutes with the sound guy trying to dial it out but it was not working. from then on, every place we played he tried putting his mouth and head that way. it almost always fed back the same way. i told him it was a good thing he didn't hold his head and mouth like that when he sang.

[Solidhex]

I've been breadboarding PNP, NPN, germ, and Si piggybacks (2n2222, 2n4401); I even tried a double piggyback (two trans stacked + a piggybacked with 3K3R), and I've stacked a Si plus the Germ.

Everything seems to sound fine.
voltages are what others report as normal.

I think I know what the fuzz face sound is (notes played in the middle of the neck with bends sound special)

So I'm wondering, as the note decays and the fuzz sound starts to fade, it goes all the way to clean - which is what is supposed to happen . . .
but I hear a crackling even with the gain set lower and with input attenuation. There is no gating nor lack of sustain.

If it was a Jfet it would sound like mis-bias.

It is not a terrible crackle, Its just a bit annoying, like a little zzzzzzzziiiiipp at the end of notes that are held for a long time.

Is a fuzz face supposed to be more graceful or does this sound like a normal fuzz face note fade?

  I know the sound you're refering to. I really only find it in silicon versions of the Fuzz Face. You should find that rolling off your fuzz knob just a tiny bit will eliminate that sound. You'll lose a tiny bit of fuzz but there should be plenty to spare on a silicon FF.
  If your fuzz face isn't cleaning up by rolling off the guitar volume your bias is wrong as mentioned previously.

--Brad

[Gus]

The feedback resistor helps set the gain of the first stage of a FF type circuit.

Google inverting opamp circuits.  Note how the gain when driven by a low resistance source is close to the out to - input  R divided by the input R.  The input R is the guitar resistance, inductance, and cap with a voltage source diving it if you want to sim it.
Now the first stage of the FF type circuit is a kind of circuit like that
The feedback is from the collector of the first transistor to the base(the Q2 emitter is a Vbe  voltage drop, buffered, non inverting signal same as the collector) and the input resistor is the guitar

One of the BIG differences is the FF first transistor has very limited open loop gain(this is part of why people pick different ones) and the inverting opamp has lots of open loop gain and a very close to 0 ohm summing node at the - input.

So a 47K should allow more control via the guitar volume control by having less closed loop gain.

The noise.  I would try what R.G. posted clean up the power supply and use a scope to look at the waveforms at different parts of the circuit.  Also short wires at 90 degree angles if you can for the input and open wiring.   Signals in wires have less coupling if the wires cross at 90 degrees.

[kvb]

thanks for the good input, all.

The main reason I asked the question in the first place is because I hear the fizz at all settings - low gain, low input volume, resistor in series with the input. So then it comes down to me not knowing what to expect in the first place.

I suppose I'll have to provide some sound clips when I can.

i think there is some background fizz in a lot of signals, but people aren't really listening for it.

but once you notice it, you turn into a sleuth for fizz and artifacts.

Yup, maybe I'm being too picky.


- I have noticed the high frequency oscilations; putting my finger on the trim pot eliminated it, so I tried a different type of trimmer.  I figured that some of these problems could be breadboard related. I will certainly solder up a board next.




Aw, Man - now I have to get a scope?!
I'm trying to avoid becoming a "waveform sleuth"