BAJA SLO MkII overdive pedal project 040218  [documentation]

Original effects with schematics, layouts and instructions, freely contributed by members or found in publications. Cannot be used for commercial purposes without the consent of the owners of the copyright.
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287m
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Post by 287m »

Wowsshhh. Finally, my favorite circuit.
Shit, out of njfet. Why this come after place order :scratch:

didnt think fit in 1590B :| unless 9mm pots came.
Image

Thanks Baja!
plush wrote:
287m wrote: or where the best position to experiment?
Between clipping diodes and output buffer. Don't forget to decouple.

If any volume drop occurs, you can replace output buffer with a power booster.
Or add another gain stage to look like this: ->[clipping diodes]->[buffer/amplifier]->[tonestack]->[output buffer/amplifier]->[volume knob]

You can find classic soldano tonestack in gewgl.
latest build, stacked with baxandall tmb style. Im not satisfied, but he said good enough. :D

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mkenny17
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Post by mkenny17 »

bump. still waiting for PCB Layout or Vero Layout for the MkIII SLO Overdrive :D

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FiveseveN
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Post by FiveseveN »

mkenny17 wrote: 17 May 2020, 11:22 still waiting
WTF is keeping you from making one? If you don't know how, take it as an opportunity to learn.
Ignorance more frequently begets confidence than does knowledge. (Charles Darwin)

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mkenny17
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Post by mkenny17 »

FiveseveN wrote: 17 May 2020, 13:46
mkenny17 wrote: 17 May 2020, 11:22 still waiting
WTF is keeping you from making one? If you don't know how, take it as an opportunity to learn.
well yeah, thanks for the advice. but currently as i type this i'm also learning how to make it happen.

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FiveseveN
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Post by FiveseveN »

Alright, now we're talking. What software are you working with? I've been meaning to switch to KiCad myself and it looks like there are plenty of learning resources.
Ignorance more frequently begets confidence than does knowledge. (Charles Darwin)

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rockola
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Post by rockola »

FiveseveN wrote: 17 May 2020, 19:25 Alright, now we're talking. What software are you working with? I've been meaning to switch to KiCad myself and it looks like there are plenty of learning resources.
Here's a KiCAD learning resource for you: I redrew the schematic in KiCAD, you can download it from

https://github.com/rockola/slo-overdrive

Just import the schematic to pcbnew (literally one mouse click) and lay out the PCB.

PS: there are some small cosmetic differences, notably I drew Vbias pointing up where possible, however the schematic should be 100% equivalent to bajaman's MkIII, let me know if there are errors. I also didn't include the bypass switch nor the LED.

KiCad 5 is required. Latest (and recommended) version is 5.1.6, however I'm using the development version, let me know if it doesn't open for you.

PPS: Footprints have not been assigned so there's a bit more work to get to that one mouse click.

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Post by FiveseveN »

Way to leave a guy without excuses to procrastinate! :D
I'm actually working on a hybrid (Blackstar HT style) SLO preamp so I'll probably do that one instead. There's some info about its current state in this log, under "Tube Boomer".
Maybe mkenny17 will tackle it if going for KiCad as well.
Ignorance more frequently begets confidence than does knowledge. (Charles Darwin)

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SYK0T3K
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Post by SYK0T3K »

Guys, can someone explain to me what is the need for multiple gain stages?

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bajaman
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Post by bajaman »

"Guys, can someone explain to me what is the need for multiple gain stages?"
answer: read the first post in this thread ;-)
be kind to all animals - especially human beings

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Repo
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Post by Repo »

Is there a demo of this pedal somewhere?

Thanks!

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PCBGuitarMan
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Post by PCBGuitarMan »

For the ones asking for demos check the link below: :thumbsup



This Circuit is Amazing! :worship:
I'm here to help you building great pedals.
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Check out our boutique effects PCBs at:
https://pcbguitarmania.com/

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Post by Musikermomo »

Made a layout for MKIII. Probably many mistakes, but its a start.
Last edited by Musikermomo on 12 Feb 2023, 03:37, edited 1 time in total.

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Post by Musikermomo »

Made a layout for MKIII (MKII + tonestack) [untested]. Should fit in a 1590BB Enclosure. Probably some mistakes in it, but its a start.

Schematic is from this post:
rockola wrote: 18 May 2020, 06:45 [...]
Here's a KiCAD learning resource for you: I redrew the schematic in KiCAD, you can download it from

https://github.com/rockola/slo-overdrive
[...]
SLO Overdrive MkIII.pdf
(61.46 KiB) Downloaded 174 times
slo-overdrive-F_Cu.pdf
(71.6 KiB) Downloaded 123 times
slo-overdrive-F_Silkscreen.pdf
(33.41 KiB) Downloaded 94 times
slo-overdrive_kicad.zip
(154.09 KiB) Downloaded 108 times
Last edited by Musikermomo on 13 Feb 2023, 17:14, edited 5 times in total.

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Axldeziak
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Post by Axldeziak »

Musikermomo wrote: 12 Feb 2023, 03:34 can send kicad files if someone is interested.
why not just zip the files and post it here for everyone?

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Post by Musikermomo »

Axldeziak wrote: 12 Feb 2023, 11:56
Musikermomo wrote: 12 Feb 2023, 03:34 can send kicad files if someone is interested.
why not just zip the files and post it here for everyone?
OK done, didn't know you could upload zips [smilie=a_doh.gif]

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elrengofa
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Post by elrengofa »

Hello! My name is Facundo, I'm from Argentina, and it's a bit challenging to get FET transistors here. It's even harder to find them at a good price and in original condition. That's why I'm very interested in this topology using op-amps, which are affordable and available almost anywhere. Today, I designed a PCB for the SLO MKIII circuit, but I omitted the input and output buffers, and I also didn't include the tonestack.

When testing the circuit, I noticed that the sound was intermittent, as if a noise gate were active. I assumed this could be due to the lack of an input buffer. I built a buffer using a BC547 transistor I had on hand, based on the schematic by Jack Orman at http://www.muzique.com/lab/buffers.htm (the first one with a bipolar transistor). When I placed it at the input of the SLO MKIII, it started to sound as it should, but with a quite annoying squeal. I haven't tried adding a buffer at the output to see what happens.

So, my question is: Do you think the squeal I'm hearing might be because I'm using an incorrect buffer for the required application, or could it be due to the lack of a buffer at the output?
Thank you for reading my message, and I hope it's understood clearly, as I'm using ChatGPT to translate it.

EDIT: I had a quite busy afternoon. I built a dual buffer (http://effectslayouts.blogspot.com/2016 ... uffer.html), but I didn't get any sound directly. I had a problem in the buffer circuit as well, which I managed to solve.
In the end, after spending the whole afternoon racking my brain, I could find the issue. I missed connecting two components when I designed my PCB in Eagle for the Baja SLO MKIII.
I made a bridge on the circuit board, and it started sounding wonderful.
In these days, I'm going to add a tonestack to it and test it as a preamp.

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