Paul Marossy

Possibly. Got breadboard? I think the resistor in series with the positive lead of the battery might work to some extent. Also, a control that messes with the transistor bias is bound to have some kind of affect.

And, to add to that, many of the settings will oscillate (squeal), and you can actually control the pitch as well. You could almost use it to produce a tone for testing audio circuits!

Maybe. But, you might possibly end up with more noise, though.

If you go to the Z. Vex site (zvex.com), on the Fuzz Factory page, it basically explains what all the controls do. There isn't that much more commentary to add to that...

Actually, that triangular symbol is a general block diagram symbol for an amplifier. It could be referring to a tube, transistor or an opamp in a block diagram. Somehow, it has become convention to use that to show an opamp in a schematic - I guess because there is no formal symbol for it like there is for a transistor, JFET, MOSFET, triode, diode, pentode, rectifier, etc.

On the Fuzz Factory stab (stability) control, the simple answer is that the resistor in series with the positive terminal of the 9V battery causes oscillation in the audio range. BTW, I looked at the waveforms of this circuit on my scope last night. Once again, not quite what I expected on some of the controls. What I did see is that the circuit takes a sine wave and turns it into an asymmetrical square wave. The vol, drive and gate controls all made sense to me. But, the comp control didn't quite do what I expected. I guess I don't know how to interpret compression on a scope, if that is even possible to see on a scope...

Well, that sounds like a reasonable explanation to me. I really don't understand transistors all that well. A tube triode I get, but transistors are somewhat cryptic to me.

Maybe I shouldnt have said "Fuzz Face type circuit", as the Fuzz Factory isn't based on any old design. In something like the Fuzz Factory, though, it works well. That would be an interesting experiment to try it on a Fuzz Face circuit. Quoting Paul Perry: "Some amplifiers will oscillate when there is resistance in the power supply, because of positive feedback. Where does this come from? The first time I saw this, it was a two transistor amplifier, where the current drain through the power supply resistance caused the voltage at the amplifier power input to ripple in sympathy. And, depending on the design of the circuit, this ripple can get to the input stage & if it is the right phase there, cause feedback. Note that the effect can be present without being strong enough to cause oscillation, in which case you wonder why none of the maths work!! Too much gain, input impedance nothing like you expected etc. And that is why a "flat" battery can make a different sound (as well of course as the voltage being lower)." All that to say that it may work on a Fuzz Face circuit.

You might be able to get a lot of weird noises on a Fuzz Face type circuit just by adding a variable resistor in series with the positive side of the 9V battery, as long as the circuit uses positive feedback. Similar scenario as the Z. Vex Fuzz Factory.

You might also try asking the same question at Aron's Stompbox Forum. http://www.diystompboxes.com I haven't heard of a schematic floating around for it, but someone at the stompbox forum might know of one.

I saw some of those vexters on ebay. They look cool. Not sure about the Zoom Ultra-Fuzz schematic. If it's analog, it ought to be fairly easy to build with a schematic in hand. If it's digital, well, it's quite a bit more complicated for the average DIYer. In fact, I wouldn't even attempt it, and I have built a lot of stuff in the last three years. It'd be simpler to buy one off of ebay or something.

Anyone here have a Z. Vex Fuzz Factory? If so, what's your favorite setting(s)? For single note stuff, I think this one is cool: Vol - 12:00 Gate - 2:00 Comp - 11:00 Drive - 5:00 Stability - 2:00 It's a very interesting circuit. I scratched out a schematic for it out of curiosity because I was very curious about how it works. The other thing that is kind of neat about it is that you can get some really long sustain notes, almost like a "fuzz infinite sustain" until the signal dies off enough for it to stop. Great noise toy! Z. Vex is a genious...

The 741 is a general purpose single opamp and the 4558 is a general purpose dual opamp. The other thing about different types of opamps is that some of them are BJT, such as the 4558, and some are JFET, like the TL072. The Ibanez Tube Screamer (TS808 and TS-9) used the JRC4558D. A lot of the DIY circuits use a TL072. The TL072 has a nice breakup. In most circuits, I can't tell much of a difference between a BJT and JFET opamp. But there are some circuits where you can see a definite difference between the two types with a 'scope.

Drak - Man, you have an expensive habit! Kevan - Thanks, I'm glad that you enjoyed those webpages. Maybe sometime I'll tackle something more complicated and more along the lines of "my own" design.

Yes, please do show us a picture!

I also get a lot of my tubes from thetubestore.com or ebay, which can have some good deals if you know what you're looking at.

Yep. They generally do impart a crunchy sound to a circuit when used for clipping. Different colors seem to have slight differences in the sound, too. I generally use red or green.

Oh, duh. I was thinking about the input resistor of the circuit. Here I go posting while I'm working again. Sometimes I do dumb things that way... LED stands for "Light Emitting Diode" Here's an example of an LED: Sorry for the lo fi picture. I like the way LEDs sound in the feedback loop of an opamp distortion circuit. I seem to like Ge diodes the least...

Yes. The feedback resistor is pretty much what controls the gain. The input resistor has a much smaller affect, although making it the wrong size can wreak havoc. Too big, and you start to lose the highs. The LM741 is a very noisy opamp for an audio circuit. I would use a TL071, NE5534 or an OPA134A. There are others as well, but those are probably the most popular ones. I have, however, used a 741 in some circuits, and it wasn't really a problem.

I think the body is kinda cool myself. If you take your time, and do it right, it could turn out nice. I personally would do the pickguard totally different, though...

The ceramic caps are 47pF and sound like a substitute for the 51pF cap on the PCB layout. This is so close to the original value that it doesn't make any difference. The 0.022uF cap is fine. No one really makes a 0.02 cap these days. The 2F9224 sounds like a 0.22uF cap to me. Not sure what the blue thingies are. They sound like 63V caps, though. The 1uF caps are fine. They are still rated for nearly three times the operating voltage of the circuit. They are bipolar, so it doesn't matter which way you put them on the PCB. Hope that helps.

Point well taken.

OK, Drak, you have a point. I forget that about the kind of stuff that you mention at these forums sometimes. I'll remember that in the future.

I disagree about power tube bias. It has been my experience that it isn't as big a deal as people make it out to be. Before power tubes became really expensive, people didn't care about biasing the tubes. They just popped them in there like they were changing light bulbs. Yes, it is true that your amp can get damaged if you are not careful, but it's not as likely as people would want you to believe. You can tell a lot about what is going on in the tube by observing the color/quality of the glow inside the tube without touching the bias. Tube biasing is mainly touted because it lengthens the life of your power tubes, and makes amp techs more money. The "proper" way to do it is subjective in itself, IMO. The thing that gets affected the most is the tone. The bias can make it sound its best to you, but even then, that might be "out of spec". I have built my own amps, and work on my own tube amps, so I'm not speaking in complete ignorance. Incidentally, I have restored my '74 Twin Reverb: http://www.diyguitarist.com/GuitarAmps/TwinReverb.htm Reverse engineered the Seymour Duncan Convertible and most of its modules: http://www.diyguitarist.com/GuitarAmps/Convert.htm And built three tube amps so far: http://www.diyguitarist.com/GuitarAmps/FireFly.htm http://www.diyguitarist.com/GuitarAmps/OctalFatness.htm http://www.diyguitarist.com/GuitarAmps/Spitfire.htm And I have hung out at the Ampage Guitar Amp forum quite a bit and also recently at AX84 to some extent.

So, would a rabid electric guitar shred better?! Sorry, had to.