Definitive bass-cut mod for the Boss OD-3?

[Bucksears]

I have an Aion Heliodor incoming, and I've made note of some of @Chuck D. Bones mods from other posts. I saw this one:
"If you want to reduce the muddiness caused by too much bass going into the distortion stages, then try reducing C33 instead. Do it in small steps because C33 has a lot of leverage. Leave all of those other caps at the stock values."

Just wondering if that has been verified, and/or if there is a different verified way to reduce the bass in the OD-3 circuit.

I had an actual Boss one about 4yrs ago, but didn't want to get into modding it too heavily; I'll do whatever on a DIY build, though.
Thx!

 

[jesuscrisp]

TBH, C33 and R51 (C7 and R13 in the Aion Heliodor) set the gain highpass filter cutoff at 720Hz, which I doubt would cause excessive low end but you can try for sure.

As the OD-3 has a couple of odd passive filters and other elements that aren't that common, there's definite room for experimentation and maybe no "definitive solution". Some ideas (referring to the parts numbers from the Aion project):

• There is a notch T filter and in front of the first gain stage that scoops mids around 700-ish Hz that might emphasize bass frequencies. Try lifting a leg of R7 to remove the scoop upfront. Making R7 larger can also take away some of the scoop.
• Reducing C11 MIGHT help to reduce some bassy/flubby clipping from the JFET stage, which is close to a JFET Big Muff clipping stage. Try 100n as a starting point.
• C15 can also be reduced for some slightly less "full range" boost post-gain, try 1uF.
• While at it, I'd also remove the diodes D2/D3 as they really serve no purpose in my mind.
• 2 consecutive input buffers are also kind of stupid if we're being honest here, not sure why Aion kept that in the build...

 

[jwin615]

You can take Chuck's advice and circuit analysis as sound. One of the better elctron manipulatora around.

 

[Chuck D. Bones]

I have an Aion Heliodor incoming, and I've made note of some of @Chuck D. Bones mods from other posts. I saw this one:
"If you want to reduce the muddiness caused by too much bass going into the distortion stages, then try reducing C33 instead. Do it in small steps because C33 has a lot of leverage. Leave all of those other caps at the stock values."

Just wondering if that has been verified, and/or if there is a different verified way to reduce the bass in the OD-3 circuit.

I had an actual Boss one about 4yrs ago, but didn't want to get into modding it too heavily; I'll do whatever on a DIY build, though.
Thx!

Try putting an EQ pedal in front of the OD-3 and use that to dial-in the desired bass cut. That will tell you how much bass cut you need to achieve the desired tone. Once we know that, we will be better informed on how to mod the OD-3 to your liking.

I stand by my recommendation of reducing C33. How much reduction depends on your requirements.

 

[Bucksears]

Thanks @Chuck D. Bones
With work & the holidays in full swing until the EOY, I'll likely start back building in January.
I bought a few from Aion and PPCB during the Black Friday sales, but these are all 'new builds' and will go to the back of the line until other stuff is done.

 

[MattG]

Try putting an EQ pedal in front of the OD-3 and use that to dial-in the desired bass cut. That will tell you how much bass cut you need to achieve the desired tone. Once we know that, we will be better informed on how to mod the OD-3 to your liking.

I would suggest trying an EQ both in front of and behind the OD-3, you might prefer pre- or post-drive bass cut. I haven't yet tried Chuck's C33 mod, but I've tried other random OD-3 bass reduction mods, and didn't like them because while they did reduce bass, they also reduced some of the mojo of the pedal. (I can't remember what the mods were offhand, but they were definitely before C33 in the circuit.)

I've actually been hesitant to do the C33 mod, only because I'm asking myself why I need to cut bass. When I'm playing by myself, as long as the drive is below 1:00ish, I think the tonal balance is perfect. At least with single coils, which I use almost exclusively (haven't played humbuckers through the OD3 in a long time). When the drive starts to get well into the latter half of the gain knob sweep, I do think it would benefit from some increased bass tightness. But I prefer it in the lower gain realm anyway (in fact, I did Chuck's r38 gain reduction mod (reduce 3k3 to 1k)) on both my real OD-3 and my Heliodor.

FWIW, it's been a while since I've used my OD-3 with the band, so Monday night at practice, I used my Heliodor exclusively for dirt. It sounded great!

Check out this if you haven't seen it already: Guitar Pedals Visualized: Boss OD-3. To me, those graphs suggest the OD-3 is fairly neutral (in the guitar's range), and arguably actually has a slight mid emphasis.

 

[jesuscrisp]

Those curves can be deceiving though. In my experience what LOOKS flat can in fact sound or feel scooped, especially with distortion involved. Plus those curves only show you the final frequency response. A pedal could have the same signature with high bass early in the circuit that is cut later or late in the circuit after an initial cut and respond completely differently.

 

[Chuck D. Bones]

Agreed. The OD-3 has tone shaping before and after every stage and distortion occurs in two different stages. Looking at the end-to-end freq response of a non-linear circuit is not very informative. You have to listen to how a note or chord blooms and decays to appreciate the tone of a dirt pedal.