Dung Beetle

MattG

Well-known member
Build Rating
3.00 star(s)
I just finished my Dung Beetle Fuzz. I read so much commentary about it here, and general positive commentary in other forums about the Scarab Deluxe. I only played with it a little bit yesterday, but so far, my experience is consistent with all the positive feedback! I love circuits like this, that manage to sound great, have a lot of flexibility, and use a small number of common, readily available parts.

It didn't work quite right on first power up, the output volume was super low, barely audible. First I checked all component values, they were good. So then I took it out of the enclosure for further debugging, and immediately saw the problem: I had originally used one of those ribbon cables between the footswitch and main PCB, and looks like I had moved it around too much and one of the conductors had become disconnected. I think in the future if I use those, I'll use a little hot melt glue to add some strain relief. Anyway, easy fix.

As of now, it works and sounds good, but I'm not sure the Bias knob is working like the demos I've seen. It seems to act more like a volume control: fully clockwise, the pedal just gets quieter, and from fully counter-clockwise to noon or so, I can't really hear any change. Not sure what's going on there. But based on the demos, I anticipated typically using it around noon anyway. Once I'm past the honeymoon stage, maybe I'll circle back and see if I can't figure out what's going on with that.

As a side note, in general I love the names @PedalPCB comes up with for the boards, particularly when they are puns. Even before the demos, I wanted to build the Dung Beetle for the name alone! My kids used to watch this animated show called Larva. My wife and I would sometimes watch it with them, we also found it amusing. One of the characters on that show is "Brown", who is a dung beetle. I wanted to use a picture of him with his poo ball on the pedal, but couldn't find any pictures that I thought would translate nicely to black and white (I don't have a color printer at home). So I just found a nice piece of monochrome dung beetle clip art to use. If you're wondering what the circle next to the footswitch is for: when I created the waterslide decal, I started with a previous design. The previous design had the LED right next to the footswitch, and I forgot to remove that circle when I updated it for the Dung Beetle. I didn't notice until the waterslide process was done, so it stays.

So I'm giving myself three stars for this build. The PCB itself is great, it's myself I'm dinging: aesthetic oversight on the decal, having to re-work the switch-PCB wiring, and an as-of-yet undetermined problem with the BIAS knob. But still a rockin' pedal!
 

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Chuck D. Bones

Circuit Wizard
Nice job, great write-up. I have one of these in the build queue.

BTW, it's normal for the BIAS control to change the volume when it's rotated.

You have a 7.5K resistor installed for R11 (it's that big-ass 1W resistor). I was going to ding you 1/2 a star for using a 1W resistor. ;) It gets better: R11 is supposed to be 750Ω. That's why the BIAS control is not working properly. I'm afraid that will cost you a star, my friend. :cool:
 

MattG

Well-known member
:oops: LOL, I need to stop saying things like, "First I checked all component values, they were good." Clearly my so-called checking skills could use a little work.

But seriously, thank you! At the risk of pulverizing what little shred of dignity I might have left: I actually went back and checked all those values at least one other time! That gets another oops emoji :oops: At least I'm consistent?

However, ignoring the wrong value for a second, I think I should be given an extra 1/2 star for using that 1W - it came from my parts collection. Better for my wallet and the environment to use what I have on hand. I actually get a little giddy when I work on a PCB that has a lot of free space (like the Dung Beetle) - I have a fair number of random parts that are deliciously overkill for use in pedals, from long-forgotten projects of yesteryear. Nice to find them a useful home.
 
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