This week on the Breadboard: The Hybrid Fuzz Driver Deluxe

[Chuck D. Bones]

Gator and I were discussing a couple of fuzzes he wanted to modify and I noticed that they had a similar topology to the Skreddy Holy Trinity: Lunar Module, Screw Driver and Hybrid Fuzz Driver. So I breadboarded the HFD and started making mods. Here's the result. It's got six, count 'em, six knobs! And they all do something good. I went back to a BJT input stage because it interacts well with the guitar. Very responsive to the Volume knob. I kept the HFD's MID BOOST knob, renaming it GAIN. As GAIN is turned up, the mids become more and more focused. Some component value changes give the FUZZ control more range. I added a cut-only MID control, a pair of buffers (Q4 & Q5) and a BMP-style TREBLE control that provides both cut and boost in the treble range. I've tried both AC127 & MP38A for Q3. They both work well. In a pinch, a low-gain Si tranny will work there too.


The 1st stage is at the bottom right. 2nd stage (Q2 & Q3) is top right. Q3 is an MP38A. Bias Trim is to the left of Q3. MID circuit and Q4 buffer are top center. Q5 and TREBLE circuit are top left. Spare AC127 is bottom center. Note how I use short jumpers to restrain the long wires.

Knobs (L-R): LEVEL - TREBLE - MID - BASS - FUZZ - GAIN


I'm working on a better pedal name...

 

[jwin615]

The Skreddy Trinity Fuzz Ultimation
Or the STFU.
Well tweaked Chuck!

 

[The Gator]

If you're looking for something to breadboard I highly recommend this! With the Gain(midboost)dimed, and the fuzz between 9 and noon, can use your guitar's volume to make dramatic changes to the amount of overall clipping. Great for soloing!
It also does the knoppfler money for nothing sound to a tee!
There is a wide range of sounds available with this circuit.
A new name?
Hmmm...

 

[Chuck D. Bones]

Is anyone interested in a version without the MID cut knob? Saves six parts, including the MID pot.

 

[MattG]

I built all three of the "holy trinity" a few years ago... and I still have a Yankee Screwdriver Deluxe Turbo PCB in my "needs debugging" pile.

But I've been rocking the Animals Diamond Peak circuit for over a year now, which is a record for me.

So I'll definitely want to give this circuit a try.

Is anyone interested in a version without the MID cut knob? Saves six parts, including the MID pot.

In terms of midrange, how does your Deluxe compare to the stock HFD? With the usual caveats that apply to long-term aural memory, I seem to recall the stock HFD was pretty flat, possibly even mid-scooped. If you think the mid cut knob might be superfluous, maybe it could be a switch (ala the your modified Dark Esbat/Spark Booster), or an internal trimpot?

Also: BJT input. For the Animals Diamond Peak, your original schematic had a BJT and then you switched to JFET. I've made several PCBs for this circuit now, and I did make one with the BJT input. Granted, several variables were changed, but the BJT input version was noticeably noisier than all the JFET input versions.

Anyway, definitely eager to try this out!

Edit: and I’ve got $100 says @cooder will have a working build of this circuit with his custom PCB before I wake up tomorrow morning!

 

[Chuck D. Bones]

The stock HFD is fairly flat with MID BOOST below 3 (10:00). Above that, the bass rolls off more and more. The HFD Deluxe has more feedback around Q1, which does two things: 1) it lowers the input impedance as GAIN is turned up and 2) it reduces the treble content as GAIN is turned up. With the bass & treble both rolled off when GAIN is dimed, what's left is plenty of midrange. Lowering the input impedance reduces pickup brightness and increases sensitivity to the guitar's Volume knob.

The MID knob allows us to reduce the midrange focus when GAIN is dimed, or to create a scooped tone. When MID is dimed, there is no mid cut.

JFETs are quieter than BJTs when the source is high impedance, like guitar pickups. However, I'm not detecting any noise with the BJT input on my breadboard. Make sure you're using a low-noise BJT such as BC109C, BC549C, MPSA18, 2N5089 or 2N5210.

Cooder has an unfair advantage by being on the other side of the International Date Line. He's always a day ahead of me.

 

[szukalski]

From the sounds of it, the mids is useful (though it'd be useful to use that 6th position for the LED). Bypassing it is just R10/TR1 to Q4, right?

C3 is tantalum, does that matter? I thought it wasn't audio signal being passed forward, rather just dumped to ground?

 

[Chuck D. Bones]

To delete the MID filter, remove C9, C10, R11, R12, VR4 and Q4. Connect the junction of TR1 & R10 to the junction of C11 & R13. We could leave Q4 and R12 in, but with the mid filter gone, we don't need a buffer before the TREBLE network.

C3 is in the audio path. It conducts audio to ground (unless GAIN is at 0). Also, if C3 is leaky, that can be a noise source. An audio engineer pointed out to me that in circuit like this, the filter cap (C14) is also in the audio path because the circuits around Q1-Q3 have poor power supply rejection. Any signal, hum or noise on the power rail will couple into the audio path via R5, R9 & TR1+R10.

The LED can go pretty much anywhere.

 

[szukalski]

Thanks for those interesting tidbits. I had assumed that because the audio was going to ground that I didn't need to care about it so much and I could prioritise the shortest traces on the audio path going through to out. I still have some thicker books to read on this subject.

 

[MattG]

I think this is how it looks with the midcut omitted. At least at a high-level, the topology now looks a lot like the Diamond Peak/"holy trinity" circuits, but with the added output buffer. Not saying it's the same of course. The OG trinity all have the same topology but not too much sonic overlap. We'll have to keep milking this circuit until "YASF" (yet another Skreddy fuzz) becomes common vernacular.



Edit: As for the option of using low-gain silicon for Q3, how low is low enough?

 

[Chuck D. Bones]

Edit: As for the option of using low-gain silicon for Q3, how low is low enough?

It's up to you. I built my Diamond Peak with 2N2221's. They test between 65 and 100. I put the lower gain ones in the Q3 position.

I think this is how it looks with the midcut omitted.

That's right. Make sure your BC549's are BC549C.

I recommend breadboarding it with the MID filter and see how you like it. Setting MID to 10 is the same as removing the MID filter, so it's easy to do an A/B comparison. If all you want is a warm tone, then you won't need the MID filter. If you're looking for something more aggressive, then the MID cut will help.

We'll have to keep milking this circuit until "YASF" (yet another Skreddy fuzz) becomes common vernacular.

I thought I was done with these until Gator sparked some renewed interest with his Hellbender circuit mods.

I do have something else cooking that's kinda related, but unless/until it tastes right, you'll have to wait to see what it is.

 

[The Gator]

I am using an sc9018 with hfe about 100.
Lower would be a bit better. It is working and sounding good though. I use BC549C for Q1, Q4 and Q5.

 

[MattG]

The bias trim TR1 10k trimpot - is there a target voltage for one of the nets? Or is it trim to taste?

 

[Chuck D. Bones]

Start with 5V on Q3-C and if that sounds good, you're done.

 

[The Gator]

This thing is the Soloist Fuzz!
Crank the gain and mid, fuzz and bass at noon, treble at 3 o'clock.
Single notes are huge!
The band I am in now is called Combo Diablo. We are working up a version of Midnight Blues like the Detroit Cobras.
I wanna use this to do the solo!

 

[cooder]

Ohhhh killing it! I better get onto it before I loose my dateline advantage haha...

 

[PedalBuilder]

Need to double check everything, but here's what I've got so far. Once I've verified that everything looks good, I'll throw a Gerber up for folks who are interested. Q1, Q4, and Q5 are BC549C. Q2 is 2N4123, and Q3 is any low-mid gain NPN germanium with an EBC pinout.

Edit: Several revisions later...

 

[Chuck D. Bones]

Looks great!

 

[The Gator]

You don't mess around! Beautiful layout.
I keep playing this breadboard circuit.
Today I was thinking about what you said about Buck Dahrma Chuck.
He is one of the most underrated rock guitarist.
Put the gain, the treble, and the mid cut at 3/4. Put the bass to half. Put the fuzz around 10 o'clock. Add you favorite delay and play Godzilla by BOC. I truly believe that buck himself would dig this circuit!
Dahrma Drive!

 

[Chuck D. Bones]

Dharma.
My favorite BOC tunes are Astronomy from Secret Treaties, Then Came the Last Days of May and Buck's Boogie from OYFOOYK. His later stuff like Harvest Moon & Dance on Stilts have some killer solos. I've seen them several times, from the Long Beach Arena way back in 75 until 2010 at the Pacific Amphitheater in Costa Mesa and some small club dates in between.