Are Guitar Knobs Universal?

Guitar Knobs Main Image

While rock, jazz, and blues are no longer the most popular genres of music internationally, the guitar is still a very persistent instrument in the sense that it’s around, it’s still cool, and it’s commonly used for popular music. There are a lot of models and brands, including different types of knobs that may or may not work with your guitar.

As I’ll point out in a second, there are a few different types of potentiometers and knobs, and some of them work better together than others. It begs the question of whether guitar knobs are universal or not? 

Guitar knobs and pots are not universal, however, knobs and potentiometers (also called pots) only come in a few different types so it’s not hard to make the right choice. There are spline split shafts, solid shafts, and then coarse and fine spline split shafts. Different knobs will fit differently.

If you’ve owned a few electric guitars in your life, you’ll know there is considerable variation in how they’re set-up and how they work. Obviously, there are more similarities than differences, but one element that separates them is the bridge. One can easily tell the difference between the classic Gibson saddle/bridge and a Floyd Rose, or the kind that Fender Strats use. It’s wise to take a look at the type of knobs and posts your instrument uses before buying one. 

Guitar Volume and Tone Knobs – How Many Kinds Are There? 

There are three very common kinds of tone and volume knobs: bell, speed, and domed. Different brands appear to use one type of knob over the other, for example, Gibson and Epiphone tend to use a lot of speed and bell knobs on their guitars. I know my Epiphone Les Paul Custom – one of the best budget-friendly guitars on ZZounds – uses them. You won’t find many domed knobs on Gibson and Epiphone, however.

Admittedly, I only have about three electric guitars at the moment, a PRS SE Custom 24, an Epiphone Les Paul Custom, and an ESP Eclipse II. While all of these instruments are quite different from each other, one thing they all have are similar shafts on top of their potentiometers. For example, you can see what the post on the ESP Eclipse II looks like in the image below.

Coarse Spline Split Shaft
This is a coarse spline split shaft – you can tell because it’s split down the center and it has 8 splines on each side

Go ahead and compare the domed knob to what can be found on the PRS SE Custom 24. Obviously, they look a lot different and how they’re fastened to the potentiometer is quite a bit different as well.

Domed knobs are usually fastened to the post with a set-screw as is pointed out with the brown arrow, whereas the bell and speed knobs are kind of just pressed on. I think it’s worth our time to actually explore the different types out there on the market.

Bell Knobs 

The first and potentially the most popular type of knobs are the bell knobs like these ones from Amazon. Fender Strats, Les Pauls, SGs, and other classic brands often use these knobs. Honestly, I think these might be my least favorite, whereas the speed knobs on the Epiphone Les Paul Custom and the domed knobs from the ESP Eclipse II are tied at first place. 

Bell knobs are extraordinarily popular and they go by other names as well including bell hats, UFO, or hut knobs, and it’s very common to find these on all of the legacy models. They’re most commonly seen in colors like gold or black, although, the ones that you can see on Stratocasters are usually solid colors like all white or all-black with the numbers on the bottom.

Speed Knobs 

Speed knobs like these from Amazon, on the other hand, are quite a bit bulkier although they don’t necessarily look like it. They’re also called barrel knobs because of the way they look. They tend to be much thicker and longer in diameter.

Personally, I find these knobs to be a lot more stylish and cool-looking than other knobs. For reference, speed knobs are about the same diameter as the bottom of the average bell-hat knob, the part that’s closest to the guitar body.

It’s common for these to be made with clear plastic with the numbers painted on the bottom. On my Epiphone Les Paul Custom, the knob itself is clear, black, slightly translucent, with the numbers painted on the bottom. One thing that’s worth mentioning is that newer guitars and manufacturers appear to have moved away from the speed and bell knobs, opting for domed knobs instead.

Domed Knobs 

Domed knobs like these (also from Amazon) are my favorite, simply because I find they’re the most modern-looking. The bell and speed knobs are like old news to me. Domed knobs have a modern feel and vibe, and they can look really cool when they’re steel-colored or even matte black. Take a look at the image below to see what these look like: 

In many cases, these knobs aren’t necessarily domed, because they sometimes have squared-off tops. It’s very common for them to be made out of steel or plastic. Mine, for example, are made out of steel and there is usually a grated material or texture on the sides of them that can be fine or very rough. 

According to Philadelphia Luther Tools, domed knobs are commonly found on Telecaster guitars, but they’re increasingly becoming more popular on the super strat type of guitars made by companies such as Ibanez, Jackson, Charvel, ESP, and more. In case you didn’t notice, all of these companies have a slight association with metal and hard rock as well. 

Domed knobs tend to look sexier and less conspicuous, which is one of the reasons why I like them. Sure, you can’t see at what point the volume or tone is set, but they look mad cool, and you’ll get a feel for where you are numerically anyway. Now that you can see all of the different types of knobs on the market, it’s time to look at what is probably the more important aspect of this topic: the actual posts or control shafts (as some people call them). 

The Posts and Control Shaft Types 

There are two main types of control shaft types, the splined split shaft and the solid shaft. The spline split shaft is literally split down the center, and it’s used for some of the older types like the Speed and Bell Hat knobs that are commonly used by Gibson, Fender, and other more classic brands. Additionally, there are more denominations of each type of potentiometer, including coarse and fine.

Spline Split Shaft 

CTS 450 Series B500K Short Split Shaft Pots Fine 24-Splines Linear Taper Potentiometer for Electric Guitar Bass, 10% Tolerance (Set of 4)

There are two kinds of split shaft knobs although both of them are 6mm in diameter and there can be more or fewer splines. Some are more coarse or finer than others, and they can be found on top of the potentiometers (which are commonly called the “pots.”)

Knobs that are usually pressed on to the shaft, typically 18-spline pot shafts, won’t fit on the 24-spline shafts. Some people might try and squeeze the shafts so that the knob can be pressed on to it, but this isn’t a wise move, and it might even cause the split shaft to break. 

Coarse Spline Split Shaft 

Alpha Mini Metric Sized A250K Guitar Pots Split Shaft Control Pots Audio Taper Potentiometers for Electric Guitar/Bass(Set of 4)

On these shafts, there are 8 different splines on each side of the shaft. In other words, there are 16 splines in total. They’re called “coarse spline” because there are less splines and therefore they tend to be much rougher than fine split shafts. Think about it, the more splines there are, the smoother it is.

Fine Spline Split Shaft 

bangdan Split Shaft Audio Taper Potentiometer Pot US Fine Spline, CTS 1meg ohm Audio Taper

Fine Spline Shafts, on the other hand, have 10 on each side totaling up to 20. In the image that you can see above, there is clearly more splines on the shaft. Really, there isn’t a huge difference between fine and coarse spline split shafts. Which one you choose is really up to you.

Solid Shaft/Post 

CTS 250K Short SOLID Shaft Audio Potentiometer/Pot - 450G Series - PAIR (2X)

Solid shafts are the least common. Usually, a solid shaft will need the knob to be fastened on to the post via a set-screw of some kind. It isn’t hard to understand why, considering there is no ridge to hold the knob there otherwise. As I’ve already mentioned, using the set-screw set-up makes the most sense to me.

My ESP Eclipse II uses a domed knob and a coarse spline split shaft, and the two are fastened together with a set screw. You grab a screwdriver, and you can loosen or tighten the knob by turning the screw left or right which will release or add pressure to the shaft. You can then take it on or off using this method. 

If you ask me, this is probably the most intuitive way of having a guitar knob, because it’s easy to put back on and take back off if you need to do so. The older knobs can be a pain to get off. With that said, you have to be careful when tightening the screw, because it’s easy to put the knob on slightly lop-sided.

Go ahead and take a look at the YouTube videos in which people show you how to get the knobs off. It’s not that easy for the knobs that aren’t fastened via a set-screw.

How to Tell the Difference Between Coarse and Fine Spline Split Shafts

To tell the difference between a coarse and fine spline split shaft, you just have to count how many splines there are on the post. “Spline,” refers to the ridges on each post, and a coarse spline split shaft has approximately eight of them on each side, whereas a fine spline split shaft has 10 on each side.

Universal Fit Knobs 

4Pcs Electric Guitar Switch Knobs Universal Volume Tone Control Knobs for Electric Guitar Musical Instrument Parts (Type B)

Some knobs are commonly called universal-fit knobs, which means they’ll fit on literally any kind of shaft, coarse or fine split shifts, or the solid shaft/posts. If you want something that you know will work, the press-on universal hats will work on almost anything, but they might not be as solid as what you would want.

By that, I mean they might not fit on as snuggly as other knobs. Personally, I would suggest trying multiple types of knobs because they’re not that expensive anyway. Send back whatever you don’t end up using.

YouTube Video Tutorial

Gear Mentioned

1) Epiphone Les Paul Custom (from ZZounds)

2) Bell Knobs (from Amazon)

3) Speed Knobs (also from Amazon)

4) Domed Knobs (again from Amazon)

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