Making control knob darker

[slowpogo]

I built DFX's Bun Runner clone. It sounds great but the tone knob on the Tone Bender side - which acts as a low-pass filter - does not quite get dark enough. Even fully clockwise some guitars/pickups are still a bit bright so I need some room to work with.

Schematic linked below. I know this is stupidly basic but I think I would need to increase the value of C8 (100n)? Would 220n be a good bet?

https://drive.google.com/file/d/1zqEsQMVecs1-njY_N86_64nTgSHcTsH3/view

[idy]

I think that tone control is two high pass filters that you pan between. One cuts all the bass, the other lets a more full range signal through. So neither will darken it. (High pass is cap in series, r to ground, low pass is r in series, cap to ground.)

If you want a low pass maybe you could either:
1)look at replacing C9 with a larger cap and a series pot
2) or change places of R9 and C8, adjusting values to mimic a big muff tone control (which pans between LP and HP.)

[PRR]

What he said. C8 is not your target.

[Mark Hammer]

Try swapping C6 and R15.  That will provide a lowpass filter whose rolloff starts a bit above 1khz.  The Tone control will now pan between a full-bandwidth and a "rounded-off" version of the signal.

Given that,however, and not being able to see the full schematic, there will need to be a DC-blocking cap in there somewhere.  As shown, both C6 and C8 prevent any DC from the circuit from escaping to the output.  Not good.

In which case, the suggestion to increase C9 is probably the smarter path.  Consider using a 3-position on-off-on to add two different caps in parallel with C9 for three different treble-cuts.

[slowpogo]

Thank you for the ideas. Given that the pedal is fully built and there's not much room to add external pots/switches, I actually tried something else. Rather than a low-pass to attenuate highs more, why not attenuate the bass less?

I increased the input cap C3 to 330n. If I understand correctly, this filters LESS bass at the input? This seems to have accomplished what I wanted. Fully clockwise, the Tone knob is now notably warmer, with the harshness tamed, but still usable. When I go CCW it lets more of the bass-cut signal to add brightness as desired.

From what I can hear, this seems to have solved my problem. Any red flags? or is this a practical mod?

[PRR]

> Any red flags? or is this a practical mod?

If you are happy, everybody is happy.

But C3 into that scheme is down 3dB at 40Hz, 1dB at 80Hz, the bottom of the guitar. I'm surprised the difference is different enough.

C16 and even C10 seem more interesting bass-chokes.

[slowpogo]

> Any red flags? or is this a practical mod?
C16 and even C10 seem more interesting bass-chokes.

What makes C16 more interesting?

[anotherjim]

Would a cap from tone pot lug 3 to ground do it? Another 15n there might be a good choice. That would let the tone pot sweep between all treble via C6 and mostly bass via C8. Semi BMP tone control.

[PRR]

What makes C16 more interesting?

Maximum fuzz effect, minimum bass. (Which is what you want to moderate unpleasant IM.)