Buddy's Breadboard and Circuit Design Notes

I recently threw together a stripboard layout I found online. This is a muff derivative called the "Ultra Stoner Mk II" by Grind Custom Fx. What called me to build this one is the DOOM switch and SHAPE control. I was thoroughly amazed at the heavy, mid-humped sounds that can come out of this, especially with a detuned guitar. I'm throwing this up here in the thread to show my trace of the layout (pardon the stain on the schematic, I was doing it during my lunch break, haha). It looks like the doom switch throws a coupling capacitor on Q3 from collector to base to remove some of the clipping. The shape control is really where I want to whip out my breadboard and try it out to see if my trace is correct. If so, I think I may have found my new favorite tone stack. I'll try this out today and report back.

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What is the value of C17? The DOOM sw is a hi-cut on the 3rd stage.

The large coupling caps let more bass get thru for more sludge.

The SHAPE control is the same as the Skreddy P19 COLOUR control, with different component values. How well does the SHAPE control work? Or is all of the action at the top end of rotation?
 
What is the value of C17? The DOOM sw is a hi-cut on the 3rd stage.

The large coupling caps let more bass get thru for more sludge.

The SHAPE control is the same as the Skreddy P19 COLOUR control, with different component values. How well does the SHAPE control work? Or is all of the action at the top end of rotation?
The layout suggests between 1n-4.7n. I'm settling toward 1n. The shape control works pretty well, but not the full range of the pot. Probably the first 2/3-3/4 and then goes away a bit in the last bit while maxing it out.
 
I've got an itch that I can't scratch. I've got a few 1590b enclosures staring at me and they need a use. My current idea is to whip up 2 One Knob Fuzzes in a single enclosure with a single switch to select a fuzz and a single volume knob. Not too difficult I think. I'll put a dpdt switch for the selector (input and output of each fuzz) going to a single volume pot. Yea, that sounds about right.

Anywho, I stumbled down the breadboarding hole of making my own one knob fuzz. Now I know what you're thinking, "There's tons of them out there!" Not really. If you google one knob fuzzes you'll get tons of fuzz faces and DAM Meathead variants. I wanted to make something more original in the true DIY fashion. After an hour or two going back and forth with work (quiet work day but have things to do), I managed to put something together that I really like that I want to share with you all.

Behold, the NUT FUZZ. In more simpler terms, this is a shunt feedback amplifier into an asymmetrical BMP clipping stage. Of course you can build this on any sized breadboard since it's just a one knobber.

This circuit is incredibly interactive with your guitar knobs. With everything maxxed out you get a lot of low end coming through with the signal hitting the BJT's HARD and almost to the point where gating occurs, but not quite. A high gain fuzz/drone sound for sure! As you turn down your guitar's volume knob the gain is significantly reduced, the low end drops out, and the treble comes through a lot to hear pick attack. To reduce the treble further you'll need to back off your tone knob or switch to your neck pickup. With the guitar volume down significantly, almost to the point of 0, you're in the bright, low/medium gain fuzz territory. As you turn down the circuit's volume the low end starts to drop off. I tend to like it more maxxed out, but I can see others tweaking it to their tastes. Maybe some day I'll make this into a PCB, but need to learn the software first. Another day, i guess.

I haven't built this on vero yet, but I took the time to make a layout this afternoon. This will probably be my project tomorrow on my day off before Thanksgiving. If you make this (and I hope you do or at least breadboard it), you'll have a standing resistor and a standing capacitor but you can counter that by just bending the leads a bit to make them more flush with the stripboard. The next one knobber I make I'll decide whether or not to separate the layouts or combine them to fit in the enclosure.

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Another cool BtR creation!
It's pretty damned close to the first half of a BMP. I don't like the bias scheme on the 1st stage because it's too dependent on HFE. I understand why you do it, but an LPB with the right resistor values will get you the same AC behavior with better DC stability. Just takes 2 more resistors.

I encourage you to try larger caps for C1 & C2 because it's not just about bass response. With larger caps, the bias varies as the caps accumulated DC when the circuit is driven hard. The bias shifting back and forth can cause gating and abrupt changes in timbre.

You can always put R1 & C3 in diagonally, then they don't have to stand up. Just sayin'.
 
Another cool BtR creation!
It's pretty damned close to the first half of a BMP. I don't like the bias scheme on the 1st stage because it's too dependent on HFE. I understand why you do it, but an LPB with the right resistor values will get you the same AC behavior with better DC stability. Just takes 2 more resistors.

I encourage you to try larger caps for C1 & C2 because it's not just about bass response. With larger caps, the bias varies as the caps accumulated DC when the circuit is driven hard. The bias shifting back and forth can cause gating and abrupt changes in timbre.

You can always put R1 & C3 in diagonally, then they don't have to stand up. Just sayin'.
I tried many times altering C1 and C2, both in the standalone first stage and then again once the full circuit was complete. I didn't like the bass response at all using anything bigger (REALLY wanted to use 100nf). It just got too muddled. I did notice some timbre changes while testing it, but they went away pretty quickly and didn't come back, so I just wrote it off.
 
A lot of the guys here, including Robert, use DIPtrace. There is a free version for non-commercial used. I've fooled around with it a bit, but since there are others here who are already good at it, I usually defer to them. Fig knows where to order boards.
 
OK, I breadboarded it and it sounds pretty good. Very bottom-heavy. I have to wind my guitar's Volume control all the way down to 1 to get anywhere close to clean. I'm going to install a FUZZ control, similar to the Arctic White Fuzz, to tailor the gain and guitar Volume response. Yes, I realize it won't be a One Knob Fuzz anymore.
 
OK, I breadboarded it and it sounds pretty good. Very bottom-heavy. I have to wind my guitar's Volume control all the way down to 1 to get anywhere close to clean. I'm going to install a FUZZ control, similar to the Arctic White Fuzz, to tailor the gain and guitar Volume response. Yes, I realize it won't be a One Knob Fuzz anymore.
I agree it’s bottom heavy, but not at the point where it’s unusable. The volume controls on both ends tame it as you turn it down. IMO this makes a good doom/drone sound
 
Breadboarding and playing thru the Fuzz Nuts got me to listen to two of my 2-transistor fuzzes for comparison: Piccola Figa & Folk Fuzz Deluxe. They too are fairly bottom-heavy. All have different tones and to me, sound better with single-coils.
In your opinion is my Nut Fuzz a one trick pony that only I can enjoy or is there potential for others to appreciate it? I'm trying to determine if I like this because of "Look what I made!" or because it's actually decent to someone who's not me.
 
I think anyone interested in the Fuzz Nuts should build it and decide for themselves. For every dirt pedal, there will be someone who loves it and someone who hates it. I'm somewhere in-between. You invent cool stuff. My comments were just that, comments.

My breadboard had a lotta hum, but I chalked that up to the fact that it was on a breadboard with long wires and no shielding.
 
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