The Week on the Breadboard: Sabbra Cadabra

[Laundryroom David]

Dang i havent gotten around to this yet! You just amped me up! I cant wait to hear what this sounds like

Strap your head on. It’s fun!

 

[fydo]

I hope this isn't a silly question, but is it possible to build this Boneyard version using the PPCB board, but with the different component values subbed in? Very curious to hear the improvements you've made!

 

[Feral Feline]

I hope this isn't a silly question, but is it possible to build this Boneyard version using the PPCB board, but with the different component values subbed in? Very curious to hear the improvements you've made!

Hmmm...

Working through the schematics:

C4 & R5 are swapped
PPCB Q3 and several associated surrounding components are eliminated (effectively turning a mu-amp into a single JFET gain-stage)
PPCB C8 has an added resistor ...


I would say the CDB-mod is definitely doable on the PPCB board, with some jumpers and paying close attention to details — might not look pretty, but I would definitely attempt it.

 

[Chuck D. Bones]

Yes. A few parts removed, a few parts changed and a jumper here and there will do it. The order of C4 & R5 is not important. My schematic reflects how I built the breadboard, but either order for C4 & R5 works and sounds the same. The trickiest bit is is replacing R22 with a trimpot, but it's all doable for the experienced modder.

A few tips to make the mod easier and maximize the likelihood of success:

Mark-up the PPCB assembly drawing with the mods. Double-check that.

Go slowly. Before soldering, verify that the installed parts are correct.

Use the correct JFETs. They don't have to be matched, but they do need to be the real deal.

Build just the first stage, test it and when it's working right, build the 2nd stage and test that. Repeat for the subsequent stages. The earlier you discover a problem, the easier it is to troubleshoot and fix.

 

[fydo]

Thank you for the information, @Feral Feline and @Chuck D. Bones. I appreciate it! I think I'll add this to my ever-expanding list of pedals I want to build.

 

[Laundryroom David]

Thank you for the information, @Feral Feline and @Chuck D. Bones. I appreciate it! I think I'll add this to my ever-expanding list of pedals I want to build.

I have a ppcb sabbath board incoming. Going to try my hand as well. I am loving this circuit.

 

[Smrtokvitek]

I made a layout. It is not proven. I may polish it a bit. Resistors could fit CMF/RN55 or 0204 SMD MELF. Caps are 5mm for foil and 5mm with 2mm spacing for electrolytic ones. I have used Mosfet polarity protection (which can be bypassed with a jumper). There is also a trimmer in place of R19 and R8 to set a bias.

I am not sure about the LED position and about the spacing of pots in general.

 

[Chuck D. Bones]

I recommend using the same hole patterns the PedalPCB boards. That way, pre-drilled PedalPCB boxes from Taya will work.

I recommend putting resistors in series with trimmers for two reasons.
1. You will never dial the trimmers anywhere close to zero resistance.
2. Those of us that don't like trimmers have a place to install a fixed resistor.

I suggest a 10K trimmer + 4.7K resistor for R8.
for the R18 / R19 trimmer, connect pin 3 of the trimmer to R19, pin 2 to Q5-G and pin 1 to R18. 250K is a good value for the trimmer, but 500K will do if that's all you have.

 

[Smrtokvitek]

I recommend using the same hole patterns the PedalPCB boards. That way, pre-drilled PedalPCB boxes from Taya will work.

I recommend putting resistors in series with trimmers for two reasons.
1. You will never dial the trimmers anywhere close to zero resistance.
2. Those of us that don't like trimmers have a place to install a fixed resistor.

I suggest a 10K trimmer + 4.7K resistor for R8.
for the R18 / R19 trimmer, connect pin 3 of the trimmer to R19, pin 2 to Q5-G and pin 1 to R18. 250K is a good value for the trimmer, but 500K will do if that's all you have.

Thanks for the suggestions! I almost forgot that there is a Tayda drill template (as I don't use it sadly). My only problem with the PPCB layout is that the knobs are too close together vertically. If I use it I can't fit 24mm knobs there. And there is also not that much space for knob labels. :-/

I will think about it. This layout is quite crowded, especially with my patterns. I would need to shuffle it a bit more.

I have the updated version (series resistors and small changes in component placement) ready so, if anyone is feeling lucky enough to try it, I can send you the gerbers. I might try it in a few months as I am currently away in a different country. And meanwhile, my stack of unfinished pedals/projects is growing.

 

[Chuck D. Bones]

Here's what it looks like when you build the CB mod on the GPCB Sabotage v2 board. The metal can with the red dot on top is an unmarked BC109C (thanks, John). The JFETs all came right off of my breadboard, so I know they have the right specs. I used a Chinese fugazi BF245C (it's more like a BF245A) for Q6. Yes, they refunded all of my money. The moral of the story is that out-of-spec JFETs can be used, you just have know what you've got and find the right spot for them.





This view shows R21 installed on the Cu side. Yeah, I could have cleaned the board before I took the pic.



The Sabotage v2 board has three less components than the Sabbra Cadabra. Referring to my schematic above, the Sabotage v2 is missing anti-pop resistor R29, "slope" resistor R21 and power filter C100. I understand that a v3 board is forthcoming. This explains why I was able to buy Sabotage boards at a deep discount. The anti-pop resistor (R29) and slope resistor (R21) are installed on the Cu side of the board. I made two trace-cuts on the top side, one for the slope resistor and one for adding the Treble Trim. The slope resistor cut is visible just above the trimpot. The Treble Trim cut is barely visible between C13 & C16. The power filter cap is installed in the spot vacated by R8 & R9. A pretty easy mod. The only kludgy bit is R9 & C8 hooked up in series.

 

[cooder]

Seems there was some trouble with pics not showing properly with this post, I tried re posting below, hopefully works now.

 

[Laundryroom David]

Here's mine, called the 'Black Box'.
It rawks big time.
Great stuff and very low noise even on full throttle. Tommi would be happy me thinks.

Homerun

 

[cooder]

Here's mine, called the 'Black Box'.
It rawks big time.
Great stuff and very low noise even on full throttle. Tommi would be happy me thinks.

 

[Chuck D. Bones]

Am I the only one who can't see the pictures?

 

[cooder]

Am I the only one who can't see the pictures?

Maybe.... maybe because the box is so black.... sigh...

 

[Chuck D. Bones]

Alright goddammit, something is FUBAR on my computer because the pix show up on my laptop. I'll clean this mess up later, I'm trying to write another opamp article.

 

[Nic]

Here's mine, called the 'Black Box'.
It rawks big time.
Great stuff and very low noise even on full throttle. Tommi would be happy me thinks.

Love the gloss graphics !

 

[Chuck D. Bones]

It is way cool. Nice work, as always. I think Mr. Iommi would approve of the artwork.

 

[steviejr92]

Those graphics are absolutely killer! I’m a sucker for black on black anything.

Incredible build quality as always!

Edit: Came back to say that solder work looks like a machine did it