Kingslayer tone/treble knob question

[fish22]

Hey gang, been awhile since I've been on the forum.

I have a Kingslayer I recently built and In my current rig, I wish I could tone down some highs.
Like, I wish the tone knob went down lower. about 9o'clock is the brightest I ever set the treble knob, but there are times when setting it to zero I wish it was even lower.

It sounds good with other rigs, but with my particular setup I'm wondering If maybe changing a cap value would help me get what I'm after. Hope that makes sense.

What do you guys think?

Cheers!

Edit:
After having a look at the schematic, I'm wondering if changing C15 (5n6) to a different value would be the trick?

Also, My knowledge of schem and tone controls are extremely limited.

[sturgeo]

Try changing R20 to 6k8, that might help if you're using the Kingslayer 1 board.

[midwayfair]

Let's take a look at how the tone control works.

It's a voltage divider that pans the function of a capacitor (C16).

When full CCW, the wiper shorts lugs 1 and 2, and puts 10K of resistance between R20 and C16. This puts the cap fully in series with R23, which is strapped across the feedback loop. What happens when we have a capacitor in a feedback loop of an op amp? It forms a low pass filter by bypassing the feedback resistor -- resulting in those frequencies never being amplified. R23 is a limiting resistor to keep it from completely shunting those frequencies, which might sound a bit dark.

When fully clockwise, the wiper shorts lugs 2 and 3, and puts 10K of resistance between R23 and C16. This effectively lets us ignore the capacitor's effect on the feedback loop, so the frequencies set by the cap won't be bypassed, and they get fully amplified. In addition, now C16 + R20 are in parallel with R21, which is an attenuating resistor between the output of IC1D and the input of IC1C. (It creates 1x gain -- R21/R22.) What happens when we put a capacitor in parallel with a resistor? We get a high-pass filter. The capacitor acts as a short for frequencies over a certain point, while the resistor slows down everything below that point. For frequencies high enough to pass through the cap, the gain is R20/R22 instead -- higher than 1x! Note that this cap is actually partially bypassing R21 all the time, because the tone knob's value + R20 never get anywhere near 100K.

At this point, if you want to modify the tone control, you need to decide what you want it to do.

1. Change the cutoff frequency: Changing the value of the capacitor will not change the AMOUNT of attenuation you get, but it will change the cutoff frequency. I'm not actually sure what it is, but maybe someone else can do the math. But this is the most common mod. Madbean has already lowered the cutoff frequency by increasing the capacitor from 3n9 in the original Klon to 5n6. Juansolo and Marauder prefer 8n2 for this cap. I go the opposite direction because I like treble -- I used a 3n3 in mine.

2. Change how much attenuation you get. This is actually tough, because we're constrained by the resistors that are already there. However, increasing R20 will mean that regardless of the position of the tone knob, the capacitor will bypass less of the high frequencies. You can also decrease R23 at the same time, to ensure that the high frequencies are amplified less.

3. Increase the tone knob's size. If you remove R23 and make the tone knob a W20, you will get a slightly better taper for the darker side of the control, but you will still have all the sounds you would have been able to get out of the original tone control when it's clockwise. This is actually what I'd go with -- you can still do #1 if you like, but the bottom line is that if you change your gear and find that your kingslayer ended up being very dark (or if you get in a situation where you find you're disappearing in a mix), you won't have lost the original sounds.