Understanding the OD-1

[jessenator]

I'm not intending this as a "which is better" ad nauseum circlejerk. I'm just curious, because there's a lot floating about out there, because I (think I) built one on the breadboard, but it doesn't line up with what I'm seeing from original schematics

Firstly, this is the one I built (yes, I saw it's modified, but I figured it was just tone control):

I ended up tweaking a few things, but let's just say this is what I built

(my new toy courtesy of a very, very generous friend)


Apparently the OG version utilized a quad op-amp, and is the foundation of the Aion Corona/Parhelion
https://aionfx.com/project/parhelion-vintage-overdrive/


Then I discovered (what I think is) the more "budget" version Boss released not long after the original



So, bottom line: wtf did I build for myself on the breadboard?    It doesn't have the quad, but doesn't have all of the other stages of the circuit the rev B model has. Is it just a derivative, op-amp series feedback clipping circuit?

[Thewintersoldier]

Much of what you are seeing in the original boss schematic is the buffered bypass switching. Here is the cliff notes of the core of the circuit. I have built both versions of the circuit and they have a different sound and feel.

Sent from my Pixel 7 using Tapatalk

[jessenator]

Much of what you are seeing in the original boss schematic is the buffered bypass switching. Here is the cliff notes of the core of the circuit. I have built both versions of the circuit and they have a different sound and feel.

Thanks for the clarification, Chris.

While I don't have an NJM chip, I have a couple of other quads I could try.

[jwin615]

While I don't have an NJM chip, I have a couple of other quads I could try.

What would the quad accomplish?
Using the other 2 as I/O buffers?

[lars]

I used that second Boss official schematic to mod a couple SD-1's to OD-1 specs. It's pretty easy to do (with the through-hole versions), and I do feel the OD-1 was a much better-sounding circuit than the SD-1 is. A key to really getting a lot out of the circuit is to mod R6 (4.7k) to a lower value, like around 2.7k. You get a lot more range out of the distortion and in fact, can go from overdrive to distortion in one pedal much better than the OS-2.

[jessenator]

Well, after several attempts on the breadboard I've gotten it to do exactly 0-to-pass-through levels on the volume pot. Drive does nothing…

Welp, time to Humpty Dumpty this thing again

Edit: this is the quad version. I'm using the Parhelion schematic for the breadboard

[WonkoTheSane]

Justin's schematic is far from accurate, no idea what that is.

You can still get NJM4136 from Mouser btw.

[jessenator]

Managed to get the OG working. Can't say I prefer it to the rev B, but opinions, preferences and all that.

Found some wonderful clipping combinations. Going to continue tinkering and seeing what I like.

[jessenator]

I used that second Boss official schematic to mod a couple SD-1's to OD-1 specs. It's pretty easy to do (with the through-hole versions), and I do feel the OD-1 was a much better-sounding circuit than the SD-1 is. A key to really getting a lot out of the circuit is to mod R6 (4.7k) to a lower value, like around 2.7k. You get a lot more range out of the distortion and in fact, can go from overdrive to distortion in one pedal much better than the OS-2.

Ope, sorry I skipped over this somehow... Thanks for the tip! I'll keep hacking it and see what good vibes I get.

You can still get NJM4136 from Mouser btw.

not seeing that one :/

[WonkoTheSane]

Oops, I meant NJM3403. Sorry about that.

[jessenator]

A key to really getting a lot out of the circuit is to mod R6 (4.7k) to a lower value, like around 2.7k. You get a lot more range out of the distortion and in fact, can go from overdrive to distortion in one pedal much better than the OS-2.

That makes a nice difference! finally tried it out on the board with a switch

[jessenator]

these are my favorite clipping combos

Code Select Expand


--->|--->|-
4148   4148
----|<"----
blue LED (d)


--">|--->|--
red LED (d) | 4001
----|<"-----
red LED (d)


--">|---">|--
red LED (d) blue LED (d)
-----|<"-----
red LED (d)


--|<---|<--
4001  D9D

(d) = diffused LED

Maybe a no brainer, but I found Ge diodes sound like hot farts in this circuit, with the exception of that last combo.

[lars]

...I found Ge diodes sound like hot farts in this circuit...

Hmm, you could have a $300-$400 circuit in there then. Now if somebody could make a pedal that makes you sound like the Shaggs...

[jessenator]

Hmm, you could have a $300-$400 circuit in there then.

ha!

I actually started looking at other circuits with this topology and I really like the Clark Gainster—almost more than the OD-1. Maybe it's (HTF do you say 'hallucination' but in regard to sound?), but the Gainster's gain/drive control doesn't boost output levels as much as the OD-1 does, and makes for a nicer, not perfect, but slightly transparent drive. The presence control is nice as well. Made alterations based on my last breadboard build of it. Here's the (un)Original Gainster OG-1

hopefully no errors, but that's what I'd get for drawing this late…

[jessenator]

.