Picking the Right Knobs for Your Modules

Whether you’re looking to spice things up with one of your existing modules or putting together your newest build, picking the right knob(s) for your synthesizer is always an exciting challenge. In this article, we’re going to take a look at a few of the key elements to look for when shopping for knobs, break down some of the common terminology, and give you all the information you need to start shopping.

The Potentiometer Shaft

Shaft Types

There are three common types of shafts you’ll see on potentiometers, and knowing which your module is equipped with is the first step to finding a compatible knob. Note that each of these three types is available in a variety of materials ranging from plastic to aluminum.

Image of a D-Shaft Potentiometer


D-Shaft potentiometers are identifiable from their distinctive cutout shape. One side of the potentiometer shaft is cut away to create a flat surface.

Image of a Knurled/Star Shaft Potentiometer

Knurled/Star Shaft

Knurled (sometimes referred to as star) shaft potentiometers have a ridged circular top, typically with a cutout through the middle.

Image of a Round Shaft Potentiometer

Round Shaft

Round shafts are a solid, smooth, and (unsurprisingly) round shaft.

What is shaft angle, and do I need to care about it?

The shaft angle refers is pretty self explanatory, and refers to the angle at which the potentiometer shaft is mounted relative to where the indicator should be. Because knobs can be mounted in almost any direction on both knurled and round shafts, this is generally only an issue when it comes to d-shaft potentiometers.

Shaft Diameter

The diameter of the shaft is the second most important part of finding the right knob. In the synthesizer world, the vast majority of knobs have a shaft diameter of 6mm, though occasionally you’ll see 6.25mm (1/4 inch) shafts pop up. This can be measured with a caliper (a relatively affordable tool) or even a ruler. If the diameter isn’t listed on a knob or potentiometer listed on our website, it’s safe to assume that it’s 6mm.

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