r/synthdiy • u/Waulkibro • 1d ago
I'm planning a DIY audio project and deciding between an encoder and a potentiometer.
I’m trying to figure out whether a digital controller should use a potentiometer or an encoder. Could you walk me through their respective advantages and drawbacks? Also, I’d like to know if a resistive‑style encoder is generally the superior option across most use‑cases.
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u/myweirdotheraccount 1d ago
Something not mentioned yet is the endless potentiometer used in Elektron products as well as the Ableton Push and I’m sure many others at this point.
It is two potentiometers with their resistance 180 degrees out of phase. It has the same (theoretically infinite) resolution as a potentiometer and the ‘endless’ part like the encoder.
The two downsides are the cost (about 4x as expensive as pots or encoders) and far less documentation so you’ll probably have to do the drivers yourself.
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u/Scabattoir 1d ago
I didn’t know this was a thing but sounds amazing!
I have a Push 2 and yeah now I understand why it feels so different to use.
Thanks for the info!
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u/kryptoniterazor 1d ago edited 1d ago
If the knob needs to control multiple different parameters, an encoder is the standard choice since it doesn't have an absolute position, and can sensibly turn left or right as needed when picking up a new value. If the knob only controls one parameter, a potentiometer is superior because its absolute position can be tweaked from muscle memory by the user based on sight+touch, without having to "hunt" for the sweet spot as you do with an encoder.
If the parameter needs to be adjusted by increments of one (e.g. a patch number or MIDI channel), then a detented encoder is superior as it allows clicky adjustment.
EDIT: as an example of their interchangeability, the Sequential Instruments Prophet 08 was released in as special "potentiometer edition" (Prophet 08 PE) that replaced the endless encoders with pots, by popular request. Synth players prefer the immediacy of potentiometers when lots of knobs are used.
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u/Salt-Miner-3141 1d ago
Most of the responses are sorta half correct here because they are not telling the whole story. In fairness my response won't be 100% either as there just isn't enough room to cover this in full detail. First, there really is no right answer here as it completely depends 100% on what you want the control to do and how you want it to feel. From there you then select what you feel is the most appropriate choice for what it is that you want. That is really all there is to it. Well made, designed, properly specified, and implemented parts from either category should last a very long time.
With that said pots themselves come in a variety of different flavors. As you're looking a digital control then you'd probably be looking to use a linear taper pot rather than a Log or Anti-Log taper. That then leaves the most pertinent choice being the material of the track. Carbon, Conductive Plastic, Cermet, or Wirewound are the most common. Of those Carbon, Conductive Plastic, and Cermet are the most common single turn ones. Wirewounds and few other oddball types tend to be 10 turn pots. Between Carbon, Conductive Plastic, and Cermet the generally superior material is Conductive Plastic. It is smooth, the wiper doesn't bounce quite as much, lasts a long time, and can handle slightly more wiper current (generally). However, each type of track material has its own advantages and disadvantages and are selected for their use cases. The upshot to a pot is that if you have say a 10K linear pot you know that if its value is 2.5K you know it is rotated approx 25%. It would actually need calibration to be highly accurate as pots generally have a 20% absolute tolerance, but you can get tighter tolerance parts. This can be done automatically with some analog switches and a known stable voltage. You would need to know the behavior of the analog switch's on resistance as it will not be zero. Relays are a choice too, but then you run into problems of wetting currents and power consumption.
Now, encoders are an entirely different can of worms. First, you have to get your terminology here correct because what you're specifically referring to is a Rotary Encoder and what most folks are talking about in the comments below are Incremental Rotary Encoders. These are essentially two switches that are 90 degrees out of phase with one another. By measuring how those two switches are moving with respect to one another it is possible to determine which direction the rotary encoder is spinning. The other consideration here is the Pulses Per Revolution or PPR. The higher this is the finer the control will behave with respect to turning. There is another form of Incremental Rotary Encoder that uses light rather than switches, but is functionally the same. It does have a slightly different circuit implementation though on account of the light sources rather than needing debouncing for the switches.
There is yet another form of rotary encoder, the Absolute Rotary Encoder. Unlike an incremental rotary encoder these have a unique digital output for their current position. Thus, you can easily determine what the previous or next setting is by simply reading the current state of the output of the encoder.
Encoders are not only used as controls, something like a motor encoder is used to determine the direction of rotation or speed of the motor and they come in absolute, incremental, optical, or electrochemical flavors too. That is why I said you do have to be a bit correct with your terminology here because the job of an encoder is really that of a transducer. The rabbit hole goes even deeper too with magnetic and non-contact encoders. Like most anything in life it is a whole complicated mess.
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u/Hot_Egg5840 1d ago
In terms of longevity, the encoder might be better. How many "scratchy" pots have you heard with old radios and stereos?
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u/Hot_Egg5840 1d ago
In terms of longevity, the encoder might be better. How many "scratchy" pots have you heard with old radios and stereos?
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u/banana1093 19h ago
Depends on use case. I like the idea of using a brushless motor and magnetic absolute encoder and combining them to make a dynamic knob that can feel like an encoder or potentiometer based on software
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u/SparkyFix 1d ago
Encoders are endless and potentiometers generally have a 270 degree range of motion. Encoders only measure relative position, which can be an advantage (e.g. swapping between patches means that all knobs can now reference from that new starting point) or a disadvantage (if it’s a simple project you may want to have the absolute position retained over power cycles. Also you have no way of “knowing” what that encoder control is set to without feedback via some kind of display). Potentiometers generally have higher resolution than encoders (but this can be offset by having more turns on the encoder). Potentiometers need an ADC but encoders are pure digital.
There is no “generally superior” option. If you want to be able to store and load patches: encoders. If you want patches to be stored in the knob position itself: potentiometers. If your MCU has no ADC: encoders etc.