This Week on the Breadboard: The DOD Carcosa

[Chuck D. Bones]

Also known as the PedalPCB Carcass Fuzz.
This beast is everything people say it is. Quite the range of tones. Something for everybody, I suppose. I built it to stock specs, except I used 2N2222s for Q4 & Q5. Believe it or not, there's nothing that I want to change. As described in the manual, BEFORE acts as a Gain control and AFTER acts as a kind of Bias control. Maximum gain on the AFTER control happens around 2:00. Both positions of the DEMHI/HALI switch work well with my Tele. I'm looking for the "Spirit in the Sky" setting. I think DEMHI mode, with BEFORE set low and AFTER set high should do it.

These setting work pretty well for general light OD tones. Switch is in the HALI position.
L-R: VOLUME - HI-CUT - DEMHI/HALI - AFTER - BEFORE

 

[Bricksnbeatles]

There was a post a few years back where someone accidentally disconnected r14 and got a strong octave effect. Gonna try that out when I get around to building one

 

[cooder]

Cool. Would be great to hear what you find with the R14 option, if the octave woks well.

 

[Feral Feline]

There was a post a few years back where someone accidentally disconnected r14 and got a strong octave effect. Gonna try that out when I get around to building one

To clarify: you mean R14 of the Carcass, not the Carcosa.


Looking at the Carcass schematic, I don't understand how lifting R14 would create the octave effect — eager to have it explained to me.

 

[Bricksnbeatles]

Found it:

Thread 'Carcass / Carcosa insane octave up'

Jul 21, 2021

I haven't seen anyone else post about it but does anyone else get really REALLY pronounced octave up on their Carcass build? I don't just mean when you've got the controls boosted, I mean ALL the time. It similar to running a Green Ringer in front of it. I kept watching video demos online but they always have the volume cranked going into a dirty amp so I figured maybe that's just how it sounded with my amp. My obsession got the better of me and I ended up ordering an actual DOD unit off eBay. It just showed up and it sounds WILDLY different. No octave, very subtle and usable tones. I...

• DigitalZombie
• Replies: 13
• Forum: Troubleshooting

 

[Chuck D. Bones]

I ran sims and tried it on the bench with a sig gen. I was able to obtain an octave-up effect. Then I tried it with a guitar. Here's what I found.

With R14 disconnected, the octave up effect works best with BEFORE set around 7, AFTER set to 0. Adjust BEFORE and/or guitar volume for the best octave tone. Obviously, the neck pickup works best, but I was able to get an octave-up tone from the bridge pickup as well.

The reason it does this is that with R14 disconnected it is easy to overdrive Q3, especially with AFTER set to zero. At the bottom half of the waveform, Q3 acts as an inverter. At the top half of the waveform, Q3 saturates and does not invert the signal. This is a crude but effective way to make an octave-up signal. Although there are better ways to make an octave-up, this works amazing well in the Carcosa.

My schematic references are w.r.t. to the PPCB Carcass.

 

[Chuck D. Bones]

Alright, so I am experimenting with making the DEMHI/HALI switch a 3-position switch. Seems like a no-brainer. The 3rd position adds more bottom-end than the DEMHI setting. The jury is still out on this one.