Mongrel Fuzz- octave-down fuzz - Vero Layout

[Toney]

 Here's a little something that came to life on the breadboard.
I was mucking around with the Buzzbox circuit  http://i2.photobucket.com/albums/y16/stm88/buzzbox.png

A few component changes and 'happy accidents', then I came up with this:



It's a fuzz with a switchable octave down.

To get things going, it needs a little tuning with the trimpots, but it's very easy.
First of all set Q2's trim to around 12 o'clock (~10k from 9v rail to collector) and then with the octave switch on, tune Q1's trimpot for the best effect. The octave will "appear" at some during the pot's rotation, around 150k 9v rail to Q1's collector or 12 O'clock). Now go back to Q2's trim pot and fine tune it for the nicest sounds.

I have added a SWTC to the end but also tried it with a Big Muff type, although you'll need to tack a recovery stage on.

Notes: sound excellent when hit with a booster at the front (very muff-esque)

Will attempt to cook up a schematic soon.
Would probably be a good candidate for a clean blend.

 

[Barcode80]

Here's the schematic (I think, double check me)



I changed the input cap to .033 instead of .039 because I think .033 is more of a standard value and it shouldn't make a difference.

[Taylor]

Here's the schematic (I think, double check me)

The 4001 should be cathode to 9v, anode to ground, right?

Cool idea, Rod. Would like to hear a sound clip.

[Toney]

 Yep, that's right.
As for the input cap, 39nF was just what sounded best with my rig, so whatever flavor suits.
Also I have updated R4's placement (now ties to Tone 3 on the Vero, as it should).

[Barcode80]

Schematic corrected above, and full PDF project file with PCB layout created and uploaded (click "Download Document"):
http://www.aronnelson.com/gallery/main.php/v/barcode80/MongrelFuzz.pdf.html

[Toney]

 Wow, that was quick
Thanks Barcode!  

I have been playing around with it this afternoon, it's a lot of fun.
I decided that a decoupling cap from Q2 is probably (definitely) a good idea, so I have tacked that onto the end.

I can't decide if it sounds better with the tone control bypassed altogether, although I guess people will roll their own, as they like.
Just connect volume 3 at C5 (Line F hole18) and leave out C4, R4 and the tone pot if you want to go that way.

[Manny]

Cheers Rod, looks interesting.
I'm going to tag this onto the end of the stupidly long list of pedals I intend to try out. I need more breadboards....   

[Derringer]

Here's the schematic (I think, double check me)

The 4001 should be cathode to 9v, anode to ground, right?

Cool idea, Rod. Would like to hear a sound clip.

+1

[Brainbender]

Thanks for this!!!

[Toney]

Added a clean blend to the Vero - this:

[Barcode80]

Project pdf file has been updated with the decoupling cap, I've got the full schem drawn for the blend version but haven't done the layout yet. It is pending.

[roseblood11]

Thanks for this circuit and the layouts, Toney!

But does it really sound the same with the clean blend? I would expect that the fuzz sounds very different as it sees a low-impedance input signal now. And how does it react now if the guitars volume is turned down? Does it clean up like the first version does?

And I think it would be a further improvement to add another clean gain stage at the end, as the simple way of mixing the fuzz and the clean signal only works as long as the fuzz doesn't produce a large volume boost (as Joel Purkiss mentions...). It's interesting to use a fuzz to boost the amp a bit ... or more than a bit.

[Toney]

Good comments Roseblood.
Simple answer: I don't know yet. I haven't built the second layout, I juts 'want' to be able to blend the octave sound with clean.
I have read that a simple fix, if impedance issues arise, is to add either a 10k resistor at the input, or better still a transformer run as an inductor. I can say I have tried it with a simple tranny boost up front and it seemed to play OK with the circuit, even at low unity-ish level gain. I am hoping that the Jfet run as a buffer will not bork things up with the fuzz sound. I was considering putting a Spdt to switch the input from "direct in" to the front of the Buff 'n  blend to get around this.

Another idea was to have the buff 'n blend switchable, so the player can have either the blend or, with a few re-arrangements, run the Jfet in boost mode to spank the front end. Can't have both without another gain stage as it will end up out of phase: no blending.
Thread just below this one at the moment- here:
http://www.diystompboxes.com/smfforum/index.php?topic=88799.0

I suppose both the boost and another stage are the way to go. Guess I could do a more effective tone control that way too hmm...
Still, one thing at a time. I am waiting for someone else to breadboard the basic circuit and chime in. 

[Toney]

Hey thanks yet again Barcode for the PDF update 

[Toney]

Just build the Buff 'n Blend version.
Worked out great. I've got clean with octave mixable below it, really fun. Only addition I made was a 10k from the 10uF to the 39K. No volume imbalance at all so i guess if anyone build it they can just go ahead and jumper R10 on the layout.

 

[Barcode80]

I've got the blended layout done, I'm about to update the project file in the next few minutes to reflect both.

EDIT: Project file updated, the file has both versions with layouts.

[Toney]

A few build notes:

Tweaking R1 anywhere between 15 - 51K for you preferred basic (octave off) tone, it changes things quite a lot. If you go with a lower value, it's probably a good idea to increase R2 so the two add up somewhere near 100k, so as to give yourself plenty of reach when tuning the octave. Got some great sounds with R1 ~ 18k
Octave seem to kick in with Q1's collector resistance ~150k and Q2 ~12k

I tried a variety of transistors and a few diodes, didn't seem too picky. I ended up using a 1n60, just because I have a few more of those.
Octave is most pronounced with the neck pick up, but it's pretty meaty, not too finicky (for me at least).

Oh and I tried an LPB2 in front of it this afternoon, much synthy goodness was had.

[Toney]

I played around with a few different boosters in front of this today.
First Tim Escobedo's utility boost, then an LPB2 and finally ROG's take on it from the Whisker biscuit. That was the winner, so while I was at it, I borrowed it again for volume recovery after a Big Muff type tone control.
I also found there to be a range of interesting voicings dependent on Q1's collector bias (in the non octave mode), also found that Q2 needs to be a little higher as well to bring things out so I figured I have gone this far might as well go the whole hog.
Might as well make the boost switchable too so: if any one's up for it...

Loaded version:



Been a fun ride. 

[Cardboard Tube Samurai]

Holy crap! Did someone say "Christmas Holiday Project"!?!?

[roseblood11]

yo! It´s really amazing, how quickly you developed this, Toney! Ißll definitely build it soon...

What about another version with boost and clean blend, maybe switchable?