Restoring electronics can be a challenge. Volume controls, tone controls, and those back-of-the-chassis adjustment potentiometers can be difficult to locate. This is especially problematic as the old controls wear out and become noisy. For example, I have an old amplifier that hisses when the volume control is in the wrong position.
One potential solution is the 450 Series “Stock Pot” provided by CTS Electrocomponents. A representative example is shown in Figure 1. Flexibility is a key aspect of this series, as a variety of unique shafts may be selected for each resistor body. In this example, a type KSD4 shaft is paired with a type D252 resistor body.
Tech Tip: Click here if you are looking for a control with integral power switch.
Figure 1: Image of a CTS Stock Pot potentiometer with custom selectable shaft.
Customized potentiometers
This series is part of DigiKey’s Value Added Service. Know that DigiKey stocks both resistor bodies and shafts. When you place an order, a DigiKey technician will install the desired shaft into the desired resistor body. For example, part number 450D252-1-ND (450D252KSD4) is formed when a type KSD4 shaft is installed into a 2.5 kΩ D252 linear (D taper) body. Figure 2 shows the available options as listed in the datasheet. Figure 3 shows the shaft types.
Tech Tip: The 2-inch round shaft may be cut to length to match your needs.
Figure 2: Part numbers associated with the CTS Stock Pot series.
Tech Tip: Variable resistors are available with different tapers. Here, the term taper describes the relationship between rotary position and resistance. The Stock Pot series includes a Log (type A) as well as a linear taper. As a rule of thumb, the Log (A) taper is used for volume controls where the non-linear relationship provides a natural feel when we consider the human ear’s response to volume. See this post for more information including a practical method to empirically determine a potentiometer’s taper.
Figure 3: Shaft types available in the CTS Stock Pot series.
Parting thoughts
Please let us know if you have any question about potentiometers or if we can help you select parts for your new or existing designs.
Best wishes,
APDahlen
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About this author
Aaron Dahlen, LCDR USCG (Ret.), serves as an application engineer at DigiKey. He has a unique electronics and automation foundation built over a 27-year military career as a technician and engineer which was further enhanced by 12 years of teaching (interwoven). With an MSEE degree from Minnesota State University, Mankato, Dahlen has taught in an ABET-accredited EE program, served as the program coordinator for an EET program, and taught component-level repair to military electronics technicians. Dahlen has returned to his Northern Minnesota home and thoroughly enjoys researching and writing articles such as this.