Mondo Fuzz with sound clip

[tcobretti]

I finally perfected my Mondo Fuzz.  Yes, it's another FF, but I spent some pretty serious time tweaking this one to sound as Ge-like as possible.  The goal was to make a Si FF that sounded exactly like my Roger Mayer Classic Fuzz (made by him, not me).  After a ton of experimentation, this is what I came up with:




I know it goes against common thought to use high gain transistors, but it seemed like the only way to get to pedal to "compress" the way my CF does.  As well, the 4.7k resistor at the front seemed to contribute to the woollyness of the pedal.

In the following sound clip, I play a little so you can hear just the guitar and amp (my Burns Brian May into my Line 6 set for Plexi), then I play a lick thru the Mondo, then I play it thru the CF.  Then I play another lick thru the Mondo, then thru the CF.  I think there are three licks total, and I screw up the last one a little. 

http://aronnelson.com/gallery/albums/album72/mondo_fuzz.mp3

The CF is a tiny bit raspier, but when it got to the point where I was having trouble telling the difference when I was demoing them I was pretty stoked.

[RaceDriver205]

I like the very beginning of the clip. The rest does sound Ge like.

[John Lyons]

Tcobretti

You need to buid the skyripper. It's got all the good FF and rangemaster stuff going on and bias/misbias as well as a rip setting that variable.
If your a FF head you'll love it. Lots of in between semi and full on oscialtion setting as well.

The clips sound good and the two circuits are very close. The lead work is my fave sound , the chords are pretty woofy though, to my ear.

John

[tcobretti]

I will check the skyripper out. I'm gonna have to order some pots first!

The chords are a little woofy, but that's the way it's supposed to sound!  It's a Fuzz Face!  I could have demoed it thru a brighter amp, and that might have made it less woofy.  To me, just like I like the Sanchez and the Orpheum for their nastyness, I like the FF for it's thickness.  I don't look for an all purpose fuzz so much as I look for one that I like.

[petemoore]

  Just checking because the 10k / 1k have changed places from their 'FF' positions.
  Mondo is right, that is some thick wool on there ! Gotta love those FF type things !

[tcobretti]

Yeah, Pete I swapped those two resistors.  Have you tried that yet?  We talked about it in a thread a couple of months ago.  It boosts the output volume of the pedal.

[John Lyons]

Yeah, don't get me wrong. It's cool and thick, I just think the thick lead sound are better to my ears than the woofy chords...But it's all really in context with what your playing.
The Skyripper is a range master in front of a FF with a blend cap from .005 to 10uf at the FF input. Round and quicksand like with the 10uf and clear and more tuch sensitive with the .005, but not harsh or even like a treble boosted sound...

I have a PCB layout that I made for for the Skyripper that is verified , I just need to polish up the pot wiring chart (more like manual...Ha ha!)

John

[petemoore]

  Mondo Fuzz seems like a great way to get thick fat saturated fuzz from a nice, simple build.
  I was looking at the Skyripper today, that is quite a large, highly convoluted build, reading the schematic made me dizzy trying to figure out what is going on in it, the dual 500k, switches...
  And figured it looks like alot of work, in fact I attempted that or one very similar to that, Way over my head at the time.
  If I were to approach that now, I think I'd want a PCB, and have everything marked, many colors of wires etc., and like you say a 'manual'...or fair amount of related texts to go by...
  I opted for a 'regular' FF, I should try a Mondo Type FF, that sounds like a big kick, might be really nice to have one next to my FF [since I always end up with extra room in FF boxes], so I can go from FF to Mondo FF!

[tcobretti]

Yeah, the skyripper looks like quite a project, but I bet you can do some crazy stuff with all those knobs.  I've played with a many-knobbed Dirty Sanchez as well as a Fuzz Factory, and you can spend hours just tweaking the knobs and playing.

If you build the Mondo, I hope you enjoy it, Pete.  Bear in mind that it is supposed to sound like a Ge FF, so if you've got one or two of those sitting around already, the Mondo may be a bit of a disappointment.

[JimRayden]

Great work, Dr Mordo! I just etched the Two-Face layout and was trying to figure out the two circuits to put on there. One's certainly going to be the Mondo. Love the sound clip, exactly the sound I'm aiming for.

Now if anyone could also point me to a more chord-friendly overdrive'ish FF, I'd be thrilled.

---------
Jimbo

[tcobretti]

I'm glad you like it, Jim.

For and overdrivey FF, I'd say build a basic Si FF, use lower gain transistors, use 20k-50k for the feedback resistor, and use a smaller input cap (<1u maybe even .1u).  You may have to make the output cap bigger to fatten it back up a little.  The input cap effects the fuzziness a lot, while the output cap controls the EQ of the circuit.

[joegagan]

tcobretti,
I REALLY like the clips. you are a great player for fuzz, not everybody gets it IMO
that is a very cool sounding fuzz. i have never heard a Si fuzz sound so much like Ge. Ge is my fave, so this is a revelation.

Just goes to show that the FF platform is infinitely moddable. cool

[JimRayden]

What? No Vol pot? 

[EDIT] Can't seem to find MPSA18 around here. How much is that thing's Hfe anyway? Any similiar to 2n5088?

---------
Jimbo

[tcobretti]

Joe, I am flattered.  I consider you one of the heavyweight guys around here, and I've looked at your designs for years.  Thanks very much!

Jim, I left the pot off the schem, but I'll add it. I used a 100kA, but it might be a good idea to use a 500k to brighten things just a bit.  However, this pedal is pretty loud, and the larger pot will boost it even more, so be ready for volume!

If memory serves, MPSA18s are 800-900hfe.  More than an 5088/5089 which I think run 400-500.  Most wahs have them, so just swap your 5088s into your wah (which many think sounds better anyway) and put those MPSA18s to work! 

[JimRayden]

I'm an antiwah kind of person. Vibes and phasers for me please.

Can you suggest any other types with roughly the same Hfe?

(ooh, look at me, I have an avatar now. I can feel the identity thrust upon me )

---------
Jimbo

[Gus]

http://www.diystompboxes.com/pedals/gusFuzzFace.gif

Have you tried this yet? almost any npn Si transistor(s) drop right in.

The square face used a 2K gain pot the old vox used a 820ohm under the 1K pot.  The one above uses an external  5K and has been here for years it gates and .......

I don't like the sound of C to B caps, I like passive filters better.

I am not a fan of series input resistors.

[tcobretti]

The only transistor I know of off the top of my head with a similar HFE is BC549C which is less common. 

I just tried it with 5089s, and it worked pretty well.  It's not quite as compressed/woofy sounding, but it's actually a pretty subtle difference, and many people don't actually like their pedals to be woofy.  If you use the 5088s, you might try a 50k-100k feedback resistor.  As the resistance increases the gain increases, BUT if you want to retain the pedal's sensitivity to changes in the guitar's volume knob you don't want TOO much gain.  The coolest solution would be a trimpot so you can tweak the value to taste.

One of my favorites tricks lately is replacing a resistor with a trimpot so I can see exactly what the resistor does.

Gus:  I have seen that schem, and one of the few FF tricks I haven't tried is what you have going on with C4 there.  Next time I build a FF I'll have to try your FF out. 

[JimRayden]

What about BC550C? 549 and 559 do have a common datasheet...

http://w3.id.tue.nl/fileadmin/id/objects/E-Atelier/doc/Datasheets/Transistoren/BC549_550_4.pdf

I guess I'll try it out with 5088's first.

---------
Jimbo

[tcobretti]

Looking at the datasheets, I think I was wrong and that the bc549/550 are about the same or a little higher hfe as a 5089.

Try em both!

[Gus]

Where the resistor values came from in mine 1996 IIRC I will check my notebooks

I looked at as many FFs and schematics I could find.
I then wrote a page of notes with the different values used and made a note of the sound if I could test one
The Si vox one with the 820 ohm is a nice build If people want to clone a Si they should clone that


Then built one with a 10K in series with a 50K pot for the first collector(10k to 60K)

A 33K with a 100K pot for the feedback(33k to 133k)

A 1K gain pot with the 5K Bias pot

I then did some math and used a 100 ohm emitter with 10K collector for the 1st transistor for open loop gain control of Q1 stage  were I wanted it (what you pick transistors for) and were I like small signal transistor in the Hfe vs collector current parts of the curves.  Again the vox had a 10K but no 100 ohm emitter.  Part of the sound is the limited openloop 1st a stage gain and closed loop resistor value

Some of the magic is the limited open loop gain of a Ge transistor I reduced gain of the first transistor with the added side effect of making it a little more linear(good or bad thing depends on what you like)

The 1K, .01uf takes the "edge" off being a lowpass filter tuned by ear.

This is also the distortion section of the 3 transistor and the rocket.