We will look into the uploading issue. However, I have now made a simulation test according to the setup below. I used 250k potentiometers both for the volume and tone control.
And here comes my simulation results with full volume and full tone (low filtering).
When we use "no" filtering and maximum volume the frequency response has a cut-off frequency of 5.4kHz.
So, lets turn the tone knob to zero (full filtering). Now we have a low pass filtering effect with a cutoff frequency of approximately 600Hz and a small peak of about 350Hz. Everything looks like expected in the graph below.
Full volume and zero tone (max filtering).
Now to the interesting question what happens when we turn back the tone pot and reduce the volume.
5% Volume and full tone (low filtering)
Oh! The cutoff frequency increases to 9kHz. Does this mean that the result would be an increase of treble and that there is something wrong with the simulation? I am not sure and I need to look into this deeper.
Compared to the first figure the frequency response is quite flat before 8k. In the first graph there is a peak between 1k and 4k with its center at 3.6k. That means all partials in that range will be up to 3dB louder when we use full volume.
Lets look into the guitars treble range. The 1st string's (E4) partials are:
f0 = 329.6 Hz
f1 = 659.3 Hz
f2 = 988.9 Hz
f3 = 1318.5 Hz
f4 = 1648.1 Hz
f5 = 1977.8 Hz
f6 = 2307.4 Hz
f7 = 2637.0 Hz
f8 = 2966.6 Hz
f9 = 3296.3 Hz
f10 = 3625.9 Hz
f12 = 3625.9 Hz
f13 = 4285.2 Hz
f14 = 4614.8 Hz
The second to the 14th harmonic is actually louder when we play with full volume. @parca, do you think this could explain the phenomena? Did you get similar results when simulating?