Special Overdrive/Shin's Dumbloid - wrong resistor

[pcb rookie]

I wrongly identified 120R resistors as 100R resistors in my components inventory. I went back to the few previous builds I did and lucky enough, I only had used the wrong resistors in one project which is the Special Overdrive (Shin's Dumbloid). I always mesure my components so this one really slipped through the cracks.

It's an easy fix and I have not boxed the Special OD yet so it's more than time to replace the two 120R resistors for 100R.

Before I fix it, just curious to understand the 100R resistance role in this circuit.

Any one can help me understand it's purpose in this specific case?

Is the 20 ohms significant to impact the tone in this specific case?

Attached is the schematic. 100R is circled in red.

Link to the documentation: https://docs.pedalpcb.com/project/SpecialOD.pdf

Thanks in advance for your help and for sharing your knowledge.

 

[jesuscrisp]

You can literally leave it as is. Minimal extra resistance in the signal path but nothing worth changing at all.

 

[BuddytheReow]

You can literally leave it as is. Minimal extra resistance in the signal path but nothing worth changing at all.

Agreed. If you were to swap them out for 100s you MAY get a very slight change in tone in the output since it is part of an RC filter, but in all probability not noticeable.

 

[BuddytheReow]

Using this calculator you are changing the cutoff frequency of the output stage from 3.4kHz to 2.8kHz if you keep the 120 in there. Slightly less "sparkle" in the overall tone.

Guitar Pedals: R-C Filter Calculator

Calculate frequency cutoff for guitar effects pedals with vacuum tubes and solid state electronics. FREE calculator.

www.muzique.com

 

[jesuscrisp]

Using this calculator you are changing the cutoff frequency of the output stage from 3.4kHz to 2.8kHz if you keep the 120 in there. Slightly less "sparkle" in the overall tone.

Guitar Pedals: R-C Filter Calculator

Calculate frequency cutoff for guitar effects pedals with vacuum tubes and solid state electronics. FREE calculator.

www.muzique.com

Somehow overlooked that! Good advice, but it doesn't matter with the switch disengaged. Maybe change only that one should the switch on mode end up being slightly dark.

 

[BuddytheReow]

Good advice, but it doesn't matter with the switch disengaged.

Agreed. There will be zero difference in tone when disengaged

 

[pcb rookie]

Thank you all for commenting. Helped me understand the purpose of the R15 resistor in reference to the capacitor/switch to create a low pass filter. I didn't really realized how that worked. Useful tool by that way R-C Filter Calculator by the way once you know how that relates on the overall circuit. Thanks for sharing. It's learning experience.

Just by curiously, what the purpose of R2 on the schematic?

Since both sides of the PCB and the two resistors is still fully accessible. I'll swap them to 100R and then I won't be wondering