Fuzz for beginners

[mfunky]

I admit - I am not a Fuzz guy... yet. 10 yrs after I played through a big muff, I thought I'd give it another try. I have built various (more complex) stompboxes and I have a breadboard, so, my idea is, that maybe I can build a fuzz that I really like by choosing the components carefully. I would like to use the axis face schematics and play with resistors, caps and of course the trannies. A quick google search turned out, I can use A LOT of different ones (some of them quite pricey...):

BC108 (traditional),b, c (vor allen Dingen "c")
2n5088
BC559a
2n5550
2sc1815
2n2369a (yaff)
2n2222a
BC183 (b,c,analogman, madbean)
BC184
GET875
CV7003
OC-84
2sb415
nkt274
BC109 (madbean9
2n3904 (madbean)
BC550

Questions:

- Which ones do you recommend for trying?
- How many of each do I need to get (I read somewhere, that you need a bunch due to wide tolerances in leakage etc.)
- Any good sources (besides the usual suspects?)
- Any other schematics, you would recommend for somebody, who comes more from the amp-produced overdrive/distortion world?

Thanks,
Matthias

[Kipper4]

Use what you have in stock or buy a lucky bag.
The axis fuzz is nice.

[Mark Hammer]

One of the most common mistakes made by a lot of folks here is to treat transistors as a fixed and unique ingredient.  Their reasoning is that you could not substitute marjoram for sugar or habaneros in a recipe, simply by adjusting the balance of other ingredients.  So if it SAYS to use such-and-such a transistor, then that's what you have to use.

The truth is somewhere within commuting distance from that, but not exactly that.

The goal is to provide enough gain to a signal that it runs into serious headroom issues that result in a flattening of the peaks of the signal.  But that running-out-of-headroom can be achieved in many ways.  It is certainly helped by greater gain, but does not depend exclusively on it.  The requisite gain, and risk of insufficient headrom, can be achieved in many ways, and one of those is via the biasing of the transistor. 

In many instances, that biasing is relatively specific to the specs of the specific transistor.  The schematic may stipulate the values of the biasing components, but those are really only ballpark figures, in anticipation of roughly what a given transistor number might require.  When it comes to op-amps, the gain you get IS a clear and unambiguous function of the gain-setting resistors.  But then, op-amps are more complex beasts, internally, and designed so as to render moot any characteristics or idiosyncracies of the op-amp.  Transistors are simpler devices, with their own idiosyncracies, such that the gain you get could be a little higher or lower than what the stated biasing component values might suggest, all because of the specs of THAT transistor unit.

But the corollary to all of this is that a great many different transistors could be used to achieve the exact same end.  If we were all equally capable of calculating the required biasing components, all a schematic would need to say is "NPN transistor here" and the required gain and offset (i.e., precisely centered in the middle of the voltage swing, or asymmetrically situated) for that stage.  But sadly, most of us are not so skilled (myself included), leaving us to rely - perhaps a little too much - on the stated biasing component values, and the suggested transistor numbers.

HOWEVER... it is not wrong to ask the experts here what one would tweak in order to get transistor X, with such-and-such specs, to perform in the desired way.

[tubelectron]

mfunky,

You can try The MinuteMan Fuzz for a preliminary breadboard test. A very simple all around fuzz, which can accommodate almost any off-the-box transistors with good results.

http://www.diystompboxes.com/smfforum/index.php?topic=92997.msg797892;topicseen#msg797892

A+!

[GibsonGM]

I 2nd Axis Face, too...but I use 2N3904's, and you may need to adjust the collector resistors if you vary from the schem...get into one, following the schematic exactly - enjoy!

Then start monkeying around with the circuit!  Try other transistors, use pots on the collectors...

[deadastronaut]

use pots on the collectors...

+1..always a cool addon...

[duck_arse]

mfunky - you left out the low-power driver/power transistors - BF469/470, BD139/140 (not sure of my polarities), maybe 2N3053, probably plenty others along those lines. low gain, low fT, no Ge leakage.

[mfunky]

Thanks! I will put em on the list. I smell a huge order and weeks of tweaking! What a great way to waste your time, I love this hobby!

[R.G.]

It wouldn't hurt for you to read Distortion 101 and the whole "Technology of..." series at geofex.com.

[Transmogrifox]

It wouldn't hurt for you to read Distortion 101 and the whole "Technology of..." series at geofex.com.

+1
Excellent material with something useful for all skill levels

[mfunky]

thanks to everyone! Especially RG: like everyone here, I am a big fan of your contributions and have read many of your "technology of..." Publications. Just recently, I built a perfect wah, which would not have been possible without these!

[mfunky]

OK, I breadboarded for a while and would like to share my findings and ask some more questions: I built an Axis Face, used the stock transistors (I tried a lot of others, but the combination 2369A and BD139 really sounds nice).

BUT:

• When I roll back "Attack", the sound looses some brightness.
• When I roll back the volume on guitar, the sound gains some brightness (and cleans up very nice...)

Is this a normal behaviour for a fuzz. I decided to replace "Attack" with fixed resistors, so my fuzz is "always on ten". Everything else is done with the vol pot on the guitar

[nocentelli]

Yep, that's a fuzzface/axis face. Many people will just run their fuzz with the attack pot up full and use the guitar volume to adjust the fuzziness. That's probably the main attraction of that circuit.

[Cozybuilder]

I recently built a modified Axis Face, my solution to the loss of sparkle when rolling back the attack is to use a small bypass cap.

Check out the schematic in this posting from the "Wedgies for Everyone" thread (Q1 is 2369a):

Thanks for the kind words guys.

I built 2 of these, with a couple of changes in the coupling caps, and the reverse polarity protection. You can use a 1N4148 or other diode (forward voltage drop about 0.7V) or a BS250 (P-channel MOSFET, forward voltage drop about 0.03V).

Here is the schematic and the perf layout. This layout could easily be done as a PCB.

 

[LightSoundGeometry]

Ive been building these meathead fuzz boxes, or the basic one knob fuzzes for a few months now. they turn out and seem to work, but I can never get any voltage readings off the transistors..lol.

maybe the pedals work but dont sound proper? Sometimes I think a fuzz sounds weird and then a youtube video shows a fuzz sounding weird!! what do they mean by synth? do all fuzzes splatter or need the guitar volume rolled back some?

I am still new to the fuzz

[mfunky]

I recently built a modified Axis Face, my solution to the loss of sparkle when rolling back the attack is to use a small bypass cap.

Check out the schematic in this posting from the "Wedgies for Everyone" thread (Q1 is 2369a):

Thanks for the kind words guys.

I built 2 of these, with a couple of changes in the coupling caps, and the reverse polarity protection. You can use a 1N4148 or other diode (forward voltage drop about 0.7V) or a BS250 (P-channel MOSFET, forward voltage drop about 0.03V).

Here is the schematic and the perf layout. This layout could easily be done as a PCB.

 

...I see! ...a bypass cap in the schematics over the "smooth pot" (220 pF in series with 22k), right? I don't see a change in the "attack" section of the original schematics (I can figure out how that is done, though...). I will try to play with the other changes as well, but I am pretty sure, that my final build will just have the "thick" and "vol" control. It needs to be very small, as I plan to put it in a 1590a. With a 9V battery  :

I've build an AMZ Mini Boost in a 1590a including a battery. This was done by using smaller components (pot, switch, jacks) and a specific position of these. See here:http://www.diystompboxes.com/smfforum/index.php?topic=64752.1980. I also included a drill template (constructing this was the hardest part) - I think, that this layout could be used for other (basic) circuits as well. Circuits that qualify are:

• Maximum Size on a vero: 12x10 (vero is not a must, pcbs will work as well - 3cm x 2,7cm
• Maximum number of pots: 2 (probably more, if we move pots to the sides as well)

The one-knob-fuzz will easily fit in there, but I am wondering: Are there any other circuits (compressor, overdrive,...) that would fit in there? First one to come up with a chorus, delay or reverb will be a hero 

Test Run:


Wired up:

[GibsonGM]

Ive been building these meathead fuzz boxes, or the basic one knob fuzzes for a few months now. they turn out and seem to work, but I can never get any voltage readings off the transistors..lol.

maybe the pedals work but dont sound proper? Sometimes I think a fuzz sounds weird and then a youtube video shows a fuzz sounding weird!! what do they mean by synth? do all fuzzes splatter or need the guitar volume rolled back some?

I am still new to the fuzz

I'd say first, work on taking those readings. That'll become important to do in the future!   One probe clipped to ground, and use the other at the collector, etc.  Should be fine, as long as you have a relatively decent meter...

There are a few reasons a fuzz you build might not sound like what you're expecting, or what the sound clip sounded like.    Using the collector voltage, you often see that it's *not* what it should be, like 4.5V off a 9V circuit.   Mis-biased.   That is why I suggested using a pot in the collector leg instead of a fixed R.   

Often, what worked for the designer (or tweaker...) won't work for someone else due to component tolerances, different transistors, etc.    So, I like to build a new fuzz (or anything else, really) and look at what those voltages are.  Most important judge IS your ear tho.   If I don't like what I see (or hear) I will start adjusting collector resistance to obtain something better.

Sometimes at full input, you get what you call splatter...the signal is just too much for the transistors to work with decently. They effectively 'shut off' on peaks (someone else will have a better, more tech explanation for this kind of compression).   Turning back the vol lowers signal and brings things 'back into order'.    Maybe something is also at play with input impedance and/or blocking distortion?

"Synthy" sounds really  just mean 'less analog traditional wooden instrument sound due to the massive clipping of the signal into square waves and the generation of distortion products (harmonics) that mimic what was done inside early synthesizers".   Kind of a qualitative thing, but 5 mins on the Youtubes will clarify that!  Think, the solo parts in "America Woman" as an early synthy fuzz...

[Cozybuilder]

mfunky-
I stuck the 22K in series with the 220p to dial back the treble a bit, its more of a Germanium sound to my tin ears, you might prefer a different value (or none).

A lower C3 brought up the treble a bit, before that it was too dark (IMHO). R5 and R6 were chosen to give 4.5V at the collector. Basically, try 1K for R5, and a 10K pot for R6, adjust to 4.5 volts, play & listen, adjust the bias until you like it, and read the pot value. Add 1K for total R, and choose 2 fixed resistors that will get you very close to the total R. R5 should be near 1K (I like 1.2 - 1.5K). Don't be surprised if you wind up with under 5K total resistance needed.

The attack pot gives a lot of versatility, this is really a more important control than "smooth"- you can use a fixed R for that.

I think if you use 9mm pots you will be able to fit a 3-pot Axis Face into a 1590A with battery. You will have to be clever about the component types and locations of course- but the necessary volume is there. Good luck, I may do one also, it really is a great sounding pedal.

[duck_arse]

but the necessary volume is there. Good luck.

this. from him, of all people.

[LightSoundGeometry]

alright..I think I finally figured out how to change the collector voltage using ohms law now - 9v / r1 = collector voltage.

so now I am guessing 4.5 volts is not what you want every time because I put approx 4.5 volts on a collector and it went splat..no go