BAJA SLO MkII overdive pedal project 040218

287m · Post by **287m** » 10 Jan 2020, 14:14

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

didnt think fit in 1590B

unless 9mm pots came.

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.

mkenny17 · Post by **mkenny17** » 17 May 2020, 11:22

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

FiveseveN · Post by **FiveseveN** » 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.

mkenny17 · Post by **mkenny17** » 17 May 2020, 15:49

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.

FiveseveN · Post by **FiveseveN** » 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.

rockola · Post by **rockola** » 18 May 2020, 06:45

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.

FiveseveN · Post by **FiveseveN** » 18 May 2020, 08:16

Way to leave a guy without excuses to procrastinate!

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.

SYK0T3K · Post by **SYK0T3K** » 27 Jun 2020, 00:11

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

bajaman · Post by **bajaman** » 27 Jun 2020, 12:17

"Guys, can someone explain to me what is the need for multiple gain stages?"
answer: read the first post in this thread

Repo · Post by **Repo** » 10 Jan 2021, 19:03

Is there a demo of this pedal somewhere?

Thanks!

PCBGuitarMan · Post by **PCBGuitarMan** » 08 Jun 2021, 12:50

For the ones asking for demos check the link below:

This Circuit is Amazing! :worship:

Musikermomo · Post by **Musikermomo** » 12 Feb 2023, 03:31

~~Made a layout for MKIII. Probably many mistakes, but its a start.~~

Musikermomo · Post by **Musikermomo** » 12 Feb 2023, 03:34

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 136 times

slo-overdrive-F_Cu.pdf: (71.6 KiB) Downloaded 98 times

slo-overdrive-F_Silkscreen.pdf: (33.41 KiB) Downloaded 75 times

slo-overdrive_kicad.zip: (154.09 KiB) Downloaded 87 times

Axldeziak · Post by **Axldeziak** » 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?

Musikermomo · Post by **Musikermomo** » 13 Feb 2023, 17:10

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

elrengofa · Post by **elrengofa** » 25 Aug 2023, 21:33

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.

BAJA SLO MkII overdive pedal project 040218 [documentation]