Tone Caps: Separating Fact From Fiction

The tone control on your guitar is one of the most versatile mechanisms at your disposal for manipulating your sound.  Like the volume control, the tone control is really nothing more than a wiper potentiometer that can send as much or as little of your signal to either the output or to ground.  The difference between the volume and the tone control is the inclusion on your tone potentiometer of one small electronic component found in almost all electrical circuits no matter how complex, from everything to cell phones all the way to doorbells.  This component is known as a capacitor, and when engaged, it filters out high frequencies sending them to ground, and allows only bass frequencies to go to the output.  Over the course of the history of the electric guitar there has been a great deal of folklore about certain brands and models of capacitors and their inherent tonal qualities, so let's take a look at some of these claims and see if we can separate some of the facts from the fiction about tone capacitors and how they can contribute to your tone.

Coveted Capacitors

These Jupiter tone capacitors can be found in many vintage Fender guitar amps, but like many capacitors, they also make for great tone capacitors inside your guitar.  The coveted Jupiter capacitors are those made in the 1960's, and these are modern capacitors built with the same specifications.

Mullard "Tropical Fish" capacitors can be found in many vintage effects pedals including vintage wah pedals, but again these have made for very popular tone capacitors in electric guitars over the years.  These capacitors are a reproduction of the vintage caps.

Sprague Orange Drop capacitors can be found today in many PRS and Gibson guitars, and were used in certain Fender guitars over the years.  They are still produced and used in guitars widely.

"Bumble Bee" Capacitors, named for their striped appearance, were originally wired into many late 50's Gibson guitars including Les Paul models, and are very coveted today.  Modern replicas are being made by Emerson, and although they were not made in the 50s these are very high quality replicas.  These are more or less the same type of capacitor as the fabled "Black Beauty" capacitor made by Sprague and found in many late 50's Les Pauls as well.

Mallory capacitors are another coveted brand of capacitor widely used in vintage guitar models.  Today there are replicas made by many different manufacturers.  

While the above mentioned list of tone capacitors does not represent all the coveted vintage tone caps, all of these capacitors are still talked about online in gear forums and amongst guitarists all over the world.  It is easy to come across articles talking about the qualities of an orange drop capacitor when compared to a paper in oil capacitor, or to find stories of guitarists talking about how they swapped the stock ceramic capacitor for a vintage sprague black beauty and it completely changed the nature of their guitar. 

In order to distinguish between the actual truth behind these claims and what is merely placebo effect, let's first take a look at how to read the value of a capacitor. 

Reading The Value of a Capacitor

The value of a capacitor is always printed on its face.  Take a close look at this photo of an Emerson Paper in Oil Capacitor.
Emerson Paper In Oil Capacitor
Underneath the brand name there is two components of this capacitor's value that are listed here.  The first is the capacitance, measured in micro farads (this capacitor is rated at 0.047 micro farads) and the second is the voltage rating (this capacitor is valued at 300 volts).

The easiest aspect of a tone capacitor's rating to understand is the voltage rating.  A passive electric guitar outputs a very low voltage, sometimes even lower than one volt.  Most tone capacitors have a voltage level that is way higher than that.  This Emerson tone cap pictured above has a voltage rating of 300, which means that it can withstand up to 300 volts applied across it.  Due to the low output of a guitar pickup, this capacitor will never see anywhere near 300 volts applied across it.  Additionally, the voltage rating of a capacitor has essentially no impact on the tonal characteristics of that capacitor, but seeking out a capacitor with a higher voltage rating can directly impact the physical size or the cost of the capacitor.

The second aspect of a tone capacitors rating is its capacitance.  Capacitors with a higher value capacitance will roll off more high frequencies than those with a lower rating.  The above pictured Emerson capacitor has a capacitance of 0.047 micro farads.  Capacitors of this size can be commonly found in guitars with humbuckers, although that is by no means a hard rule.  The capacitance value of a tone capacitor makes all the difference in the world on the tonal qualities of a capacitor.  The most common sizes today are 0.022 micro farads and 0.047 micro farads, however in the past Fender and Gibson have both used much higher values such as 0.1 micro farads.  One thing that can complicate this measurement is that capacitance can either be measured in micro farads or pica farads.  For example, a capacitor with a rating of 0.001 micro farads is sometimes written as 1000 pica farads, so keep a close eye on the capacitance rating when deciding on what tone capacitor to use.  

Not only does the capacitance rating affect how much high frequencies will be rolled off by the tone control, but it also has an affect on the taper of the tone control. Depending on your guitar and what kind of pickup you are using, a higher capacitance tone cap can cause most of the rolloff to occur between 0 and 2, for example, on your tone control with not much difference between 3 to 10.  Capacitors with a lower value can often contribute to a more even taper, although again I must reiterate that this is not a hard rule.  

If you are looking to swap out your tone capacitor, it is a good idea to buy a couple of different sizes and ratings, and test them out.  You can do this by soldering leads to the lug of your tone control and connecting those leads to alligator clips.  Check out this article to learn more about how to do that:

Premier Guitar Tone Capacitor Article

Lindy Fralin also has a great video on the sound of different tone capacitor sizes, and I highly recommend checking that out.  Here it is:

Does The Material Matter?

Finally, I'd like to talk about something sort of controversial.  Does the material that a particular capacitor is made of have an affect on the tone?  The answer depends on who you are asking.  If you want my personal opinion which is informed by experience and research, but is certainly not the authoritative voice on this issue, here it is.  If two capacitors have the same value rating in terms of their capacitance but they are made from two different materials, there is no electrical reason why there would be any sort of difference of tone between the two components.  When it comes to capacitors, the tone that you're hearing does not ultimately come from the material of the capacitor, but it comes from the signal that the capacitor is allowing to pass through.  This means that if two capacitors are rated the same value, they should be allowing the same signal to pass through, and the tone should be identical.  I would however like to add one caveat to that statement.  All capacitors have what is known as a tolerance rating.  Often times, this tolerance rating is visibly printed on the face of the capacitor alongside the capacitance and voltage rating, and is measured as a percentage.  This tolerance rating tells us how much the capacitance value can vary from its nominal capacitance value written on the part.  If two capacitors of equal capacitance have different tolerance ratings, it is possible that those two capacitors can have different tonal characteristics.  This difference however, would be the result of a difference in tolerance and therefore a difference in the actual capacitance, and not related to the two capacitors being made from a different material.  

That said, I have to say that I am wrong a lot and I am never afraid to admit it.  If you disagree with me here, please feel free to comment or to reach out by email or any other way and I would love to hear your thoughts!  Thank you again as always for allowing me to be a small part of your journey with the guitar, it is a privilege that I never take for granted.

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