I guess most of you know that the value of the volume pot  affects the sound of your pickups. I already wrote a blog post on this some time ago – please refer to this to understand terms like ‘resonance peak’ and what it means for the sound. Today I will cover some more details of this phenomenon, especially with regard to Mark Knopfler’s guitar sound.

Does only the volume pot matter or the tone pot as well?

This was really a valid question for me which I was unsure about myself. Of course a smaller value tone pot – e.g. 100k instead of 250k – will act like the 250k pot set to something like ‘9’ instead of ’10’ even when turned fully up. But here I am talking about a possible effect on the height of the resonance peak of the pickup.

From a technical point of view (skip this part if this is nothing for you), I had reasons to believe that it does not, and also some reasons to believe it does. This is because the tone pot – unlike the volume pot – does not bridge the hot wire directly to ground but does so via the tone capacitor. If you measure the total load of both pots to the pickup, your meter will only show the volume pot value (this is because the capacitor does not pass DC). This was reason to believe it does not affect the resonance peak height. However, a guitar produces AC (alternate current, DC is direct current), and the tone pot passes AC more or less (depending of the AC frequency, and at the frequency where the resonace peak of a pickup sits –  some kHz – it passes AC even very well). This is reason to believe it affects the resonance peak height.

I could not find the answer easily in the web, so I simply decided to measure it myself. I found that the tone pot DOES MATTER, equally to the volume pot. For this reason, we need to look at the total load that both pots put on the pickup (two resistors in parallel – this is what the pots are – combine due to a special formula, two identical values will result to half the value – 2 x 250k to 125k – but e.g. a 250k and a 500k will result to 167k). Theoretically, the AC resistance of the tone capacitor has to be considered in the equation as well, but this results to changes < 1%, so I left it out.

Load of the guitar pots for different guitar types

Here I list the load of both pots for the various guitars that are relevant for us MK fans.

small value – soft and sweet (or muddy, depending on the other settings)
high value –  bright (or harsh, depending on the other settings)

Fender Strat (any pickup combination except middle & neck or bridge pickup only)
2 x 250k
125k

Fender Strat (bridge pickup only)
1 x 250k
250k

Fender Strat (middle  & neck pickups together)
3 x 250k
83k

Schecter Dream Machine  (Strat or Tele)
2 x 500k
250k

Fender Tele (>1967, e.g. the black Water of Love Tele)
2 x 1000K
500k

Fender Tele (<1967, e.g. Mark’s sunburst Tele Custom)
2 x 250k
125k

Les Paul (bridge or neck pickup)
2 x 500k
250k

Les Paul (bridge & neck pickup)
4 x 500k
125k

 Total load  for different guitars and effects/amps setups

Besides the load of the guitar pots, the load of other devices in the signal chain also matters. These will combine with the load from the pots following the same formula (parallel resistors). However, not all effect devices matter, only those up to the first in the chain that transforms the signal to a low output impedance (most effects will do, even when switched off, but some, e.g. the volume pedal, do not).

small value – soft and sweet (or muddy, depending on the other settings)
high value –  bright (or harsh, depending on the other settings)

Fender Strat (125k) into rack or tube amp or through Active Lead cable (1996 – 2001 tours, 1000k)
111k

Schecter (250k) into rack or tube amp or Active Lead (1000k)
200k

Live in 1979: Fender Strat (125k) into Morley volume pedal (68k) into MXR Analog Delay (500k )
40.5 k

Water of Love Tele (500k) into Morley (66k) into MXR (500k ?)
53.5k

Making Movies album: Schecter (250k) into Music Man (319k )
140k

Alchemy: Schecter (250k) into Nady Guitar Transmitter (500k ?)
166k

Studio: Fender Strat (125k) into Ernie Ball volume pedal (250k) into rack (1000k ? )
77 k

Les Paul (bridge or neck pickup) into Ernie Ball volume pedal (250k) into tube amp (1000k)
111 k

The effect is less pronounced with a Les Paul but still existing (the resonance peak is less strong than with single coils). On guitars with active pickups, e.g. the Pensa/Suhr MK 1, the pots and other loads do not matter at all.

 Can I get any benefit of this and shape the sound of my guitar with my setup

Here is a good and very short answer: yes! You can decrease the load value by simply adding a small resistor – a part for a few cents – into the signal chain to emulate other values in the list above. The resistor connects hot and ground, and can sit anywhere in the signal chain, e.g. between the hot wire and ground on the volume pot, between hot and ground at the output jack, or in the guitar cable plug.

You can use an online resistor calculator like this one to calculate the value you need. Simply put the value of your guitar alone (see list above), for your first effect(s) or amp (you will find most values in the list above as well), and for the resistor into the fields of the online calculator, and press ‘calculate’. Change the value of the resistor until you reach the target value for the sound you are looking for, found in  the second list above.

Example: you have a normal Strat (125k) that you play into a tube amp (1000k, try 500k for a non-tube amp), and want the soft MK 1979 live sound (Strat, Morley, MXR -> 40.5k). Enter 125 and 1000 into the first fields and some start value into the third, calculate, clear the result and change the resistor value until you get near 40.5. In this example you will need anything about 50k. Buy a 50k resistor – the smallest wattage, usually 0.25W will do, more will not hurt either – and put it into your guitar, or into the plug of a dedicated guitar cable for this sound.

If you want to increase the value, you can exchange the pots in your guitar, or put a standard effect device (500k or 1000k input impedance) before e.g. your passive volume pedal (250k for an Ernie Ball, 68k for a Morley). This way the volume pedal value can be neglected, only the one of the effect will matter.

I might make a future video to demonstrate the change of sound with different values, check out.