Red Fuzz build report

[jmusser]

I'm not sure exactly where this circuit came from, but here's the link  http://hem1.passagen.se/robin2/im/red_fuzz.gif  I have had this  schematic lying around for a spell, and finally decided to throw it together. This circuit is WAY HUGE! It's not so much a fuzz, as it is an over the top OD. The LEDs make it very crunchy. It has 3 controls.The "Intensity" could easily be called "Snarl". It really gives a bite and growl to this thing. The "Tone" control does a decent job, but doesn't have a massive range like a few other pedals I've made. For some reason, the fuzz seems to come out better with the effect's volume turned to about half, instead of wide open. The design called for an LF351 op amp, and a BF245C jfet. I used what I had, an LM741 and a J201. I like this one very much and it's defininately a sleeper circuit, that deserves some press. Build it, and you'll be thrilled!

[Connoisseur of Distortion]

soundclips would be awesome. it looks very easy to build, so it might end up on the heap-of-stuff-I-really-want-to-do

[jmusser]

I wish I had to hardware to do that with. I guess you'll just have to take my word for it and give it a try. If someone looks at this post that knows whose circuit this is, I'd like to give credit where credit's due. It sounded good through both my SS Amp, and my little tube amp. That's pretty rare with most of the stuff I've built. Usually a particular circuit is pretty specific to one type or the other. I think it actually sounds quite a bit like a cranked Fender Amp. You find yourself wanting to play the "La Grange" lick!

[Connoisseur of Distortion]

i am considering building it, but first i have a couple of questions...

how does it do in terms of sustain?

i assume it has fairly heavy distortion. does it feel metallic, smooth, natural, harsh...?

how does that tone control work? it doesn't look like it would be especially effective...

can it get the usual high gain tricks out? (palm mute, pinch/artificial harmonic, tapping...)

if there's anything else that really stands out, please inform. it looks like a circuit that could be built and boxed in an afternoon. unfortunately, an afternoon is one hell of a luxury to me. 

[andronico]

Yes, is a very very good effect from Robin Tomtlund (http://hem1.passagen.se/robin2/effects.htm).
I made one last january and I´m very impressed with it. 

[WGTP]

http://www.diystompboxes.com/pedals/shakahv.jpg

Here is a similiar circuit from Aron.  Also, check out his III which uses a Mu-Amp for the Jfet section.   

[jimmy54]

I built a red fuzz a few months back using a GGG PCB.  It's now one of my favorite pedals, a definite sleeper pedal.  I'd agree with the comment someone made about it being more of an OD than a fuzz.  I also find it best with the volume at 12 o'clock (there's plenty of volume boost with this pedal) and the intensity at 12-3 o'clock.  It also cleans up well with the guitar volume lowered and so can go from slightly overdriven bluesy overdrive to full on high gain.

[mac]

I've found this circuit at GGG, well recorded sound samples included, one with 1N4148, the other with leds. Both versions sound very good so a switch to select the diodes is a nice mod.
A mod I tried is a better IC biasing, something similar to the bias of the DOD250 or the MXR+, although it is not a must.
Another mod is a 100k pot instead of the 1M, decreasing the 1.8k to 180R and upping the 0.22u to 2.2uf  to have the same gain and corner freq.
In some ways it is similar to the Ibanez FatCat, a good sounding underrated pedal. The FatCat has the clipping diodes after the IC, a voltage follower transistor at the input and a better IC biasing.

mac

[jrc4558]

Hey all!
*jmusser - you may want to get a j-fet input op-amp for that thing. tl 07(6,8)1, lf 351 or any compatible kind. These have a higher slew rate, so you will have even more Krrunch!

[Mark Hammer]

I haven't built it, but essentially it is a Rat with a pair of LEDs in the feedback loop of the op-amp instead of going to ground after the op-amp.  So, a kind of "Screaming Rat".

The 1k8/220nf network provides a rolloff below 400hz, which seems kind of wimpy.  Changing 220nf to 330nf or even 470nf might be a good idea, keeping more of the bass and resulting in sturdier clipping at lower gain settings.

The 10/1meg + 1k8 network provides a gain of 562 at max.  The use of red LEDs will yield a clipping threshold of around +/-1.5v (i.e., clip when max voltage swing is about 3vAC).  Strumming a chord moderately will give you 50-80mv output (full bandwidth), as measured on your DMM.  Multiply that by 562 and you should get decent clipping for most of the note duration though things die off pretty quick after that first couple of milliseconds, yielding more restrained clipping for the rest of the note.  Folks who want buzz more than volume, should consider changing one of those LEDs for two 1N914 diodes in series (going in the same direction as the LED went).

The tone control provides single-pole lowpass filtering, with a high-end rolloff range from around 22khz at max treble to around 470hz at min treble. In view of that rather lax high-end filtering, it might be a good idea to tack on a cap in parallel with the LEDs to reduce the fizzies.  A value between 10-18pf might be good (high-end rolloff of 15.7khz, 8.7khz).

Apart from those changes, looks like it could put out quite a whomp for any unsuspecting amplifier.

[BD13UK]

As usual Mark a sublime reply !!!!!!!!!!!!!!!

[jimmy54]

I wouldn't mind building another with 1N914 diodes for a more fuzz rather than OD tone.  Even easier, how would I wire up a switch to switch between the two LEDS and two 1N914's and what kind of switch would I need?

Cheers

[mat]

I'm not sure exactly where this circuit came from, but here's the link  http://hem1.passagen.se/robin2/im/red_fuzz.gif  I have had this  schematic lying around for a spell, and finally decided to throw it together. This circuit is WAY HUGE! It's not so much a fuzz, as it is an over the top OD. The LEDs make it very crunchy. It has 3 controls.The "Intensity" could easily be called "Snarl". It really gives a bite and growl to this thing. The "Tone" control does a decent job, but doesn't have a massive range like a few other pedals I've made. For some reason, the fuzz seems to come out better with the effect's volume turned to about half, instead of wide open. The design called for an LF351 op amp, and a BF245C jfet. I used what I had, an LM741 and a J201. I like this one very much and it's defininately a sleeper circuit, that deserves some press. Build it, and you'll be thrilled!

I like it a lot too, it's the best OD pedal so far for me (with the blue magic very close). If someone want's to check my build (named 'blue red overdrive') and soundsamples go to: http://koti.welho.com/mtiilama/ and from there the 'effects' page. I did put a dip-switch to mix several leds and diodes.

mat

[jmusser]

Wow, I'm glad there were some previous builders to chime in, and of course Mark's notes on polishing mods. I will try a TL071. I believe I have a couple of those laying around. So far, the ultimate tone control I've heard, is the one for the Whisker Biscuit. I don't know of another one that swings so extreme. I will try this one with the caps Mark suggested and see if it's better. It's not bad though. At least you can tell something is happening. Other tone controls seem like they're just another knob to turn and nothing happens. This one is more of a smoothing control. I'm glad I came across this one.

[jrc4558]

As far as tone controls go, take a close look at the XXL tone control. It uses a 100k linear pot and two passive components. one is a 10k resistor, soldered between leg 3 and the wiper, and the other one is a .047µF capacitor, soldered between leg 1 and the wiper. leg 3 gets the ground and leg 1 connects to the audio path (in case of red fuzz - to the point between the C4 and C6. You will have to omin the R9 R5 and C5 if you were to try this tone control). it is a very interesting tone control, i cant quite describe it, but it does really useful things. There is a schematic somewhere around on this forum too!

[jmusser]

Thanks Andronico for the Robin Tomtland link, and thanks to Robin for the circuits. It looks like he has several on there to try.

[mac]

The additional information at GGG indicates that the source voltage Vs is about 2.6V for a 2N5457.
If a MPF102 is used Vs is near 4.5V, and for a BF245A Vs is about a volt. I like the BF245A with a 22k at the source to get around 4.2V. Besides it has more gain than the MPF102.
And for a J201??? I'd like to know the value of Vs.

The IC I used is a TL071. I guess it sounds like the LF351. Some day I'll try Joe Davisson's diode compression opamp on this circuit, and why not, a germanium instead of the fet.

A cool feature of this pedal is that when I connect it directly to the aux input of a technics audio amp i've got smooth crunchy sounds... tweeters off, of course. Nice for practice sessions and recordings.

mac