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Difference between "A" and "B" pots

Discussion in 'Pickups & Electronics [BG]' started by Teddybear, Jun 14, 2019.


  1. I thought I knew a lot about pots. I had pretty good electronics training in the Air Force but the Air Force doesn't use pots for volume or tone. In order to learn I have been checking out websites (Seymour Duncan, StewMac, CTS, etc.) and they seem to be an excellent source of information. My problem is that they may be too good. I think I am suffering from information overload. I'm not as confused as I was when I started but I still have not answered the questions I had when I began.

    I'm trying to discern the difference between volume and tone pots. Yes, I have found that they are mechanically the same but wired differently. That only brings up new questions:
    1. Does wired differently mean that they are somehow wired differently internally or by the connections that they use externally? I realize that volume pots use three connections and tone pots use two but that makes me think that they are different on the inside.
    2. I have learned that tone pots are designated "A" and volume pots are designated "B". This different designation would, again, make me think there is an internal difference between the two. When I look at product descriptions on these websites all they show is "control" pots. I have yet to see any designated either "A" or"B".
     
    Last edited: Jun 14, 2019
  2. Zoobiedood

    Zoobiedood Commercial User

    Sep 1, 2015
    Writer/Ambassador/Artist/Resident Bass Expert for Seymour Duncan
    A pot can be used for volume or tone. The A or B refers to the taper, and people have different theories about which is best for volume or tone:
    A = Audio Taper
    B = Linear taper
     
    ctmullins likes this.
  3. ctmullins

    ctmullins fueled by beer and coconut Gold Supporting Member

    Apr 18, 2008
    MS Gulf Coast
    I'm highly opinionated and extremely self-assured
    Yep. Constructed the same, but can have different tapers and different overall resistance values. Which taper to use for which application is personal preference.
     
  4. James Collins

    James Collins

    Mar 25, 2017
    Augusta, GA
    There is also a C pot which is a reverse audio taper.

    1. Wired differently means external connections.
    2. A pots with resistance that tapers logarithmically, and B pots taper linearly.

    You can use either type of pot for either situation. It is all personal preference.
     
  5. Sooooo...

    "A" pots for tone and "B" pots for volume if, and only if, they are interchangeable.
    Also, audio taper for tone control and linear taper for volume. However,
    To make matters much much worse websites that try to explain the differences in the two types of taper or try to explain what taper is give examples of the effects of the different types of taper without any explanation of what taper actually is or where it comes from.

    One cannot purchase an "A" pot or a "B" pot simply because they are not offered for sale. They are not included in any product list. I am given the impression that they do not exist.

    I am not trying to make a fool of anyone. I know you are trying to help but I am back to the point where I started: If the pots cost the same then I want to purchase the pot that is best for the application. I am beginning to believe that it is not possible to do so.
     
  6. ctmullins

    ctmullins fueled by beer and coconut Gold Supporting Member

    Apr 18, 2008
    MS Gulf Coast
    I'm highly opinionated and extremely self-assured
    “A” = Audio taper
    “B” = Linear taper

    Those are the two most common, though there are others.

    View attachment 3445983

    “Best” is, as stated, personal preference. We can’t tell you what you will like most.
     
  7. By definition this means that they are exactly the same, mechanically or otherwise. After all, that is what "the same" means.

    That is not possible if they are the same. However, do not be concerned about the contradiction. You are doing the the same as everybody else. This cannot be explained without contradictions. No, that is not quite accurate. I should have said, "This cannot be explained."
     
  8. ctmullins Thank you so much. It is kind of hard to argue with something when you have had your nose shoved in it. Now that I know the designations exist I guess it is only a matter of patience and paying attention when trying to place an order. I feel shamed but at the same time happy that what I want does exist. Again, thank you.
     
    ctmullins likes this.
  9. James Collins

    James Collins

    Mar 25, 2017
    Augusta, GA
    Warwick lists there pots as A, B, and C. Others would list them as audio/log, linear, and reverse audio/reverse log.

    They are constructed the same in that a brand will have made the actual pot the same in that all the parts are the same except the resistor.

    The three terminals are connected like this:

    1=====©=====2
    The © would be the common central terminal. All three terminals are connected across a resistor "=". This would represent the pot in the middle position.

    Turning all the way clockwise would look like this:
    1©==========2

    There is the same amount of total resistance, but the resistance is minimal between 1 and ©. It is maximum between 2 and ©.

    If you went counterclockwise the reverse would be true.
    1==========2©

    The above would be a linear pot. If you turn halfway the resistance is equal 1 to © and 2 to ©.

    A logarithmic pot will taper based on the logarithmic scale. So at halfway, it would be like:
    1=====©==================...============2

    An antilog pot will be the reverse at halfway:
    1===============...===============©=====2

    I will tell you that 100% of my Warwick's have linear volumes and a balance pot that is a stacked audio/reverse audio pot. My fender style basses have all audio pots on the tone and volume controls. It is personal preference.

    Also, a tone pot is a volume pot that is wired in such a way that primarily high frequencies are decreased from the output.

    The audio pot will in theory decrease volume in a manner consistent with how our ears perceive volume. In practice, it is not always the case. You might find that below 2 or 3 it just cuts off. In that situation a linear pot will spread out some of the volume control over a wider rotation of your potentiometer knob.
     
    4sight and Matt Liebenau like this.
  10. BlueTalon

    BlueTalon Happy Cynic

    Mar 20, 2011
    Spokane, Washington
    Endorsing Artist: Turnstyle Switch
    Think of two houses that are structurally identical but have different furniture in them. They are constructed the same. The audio taper and linear taper pots are constructed the same, in that they have the same body, spindle, etc. That's the "house." The tapers, meaning the varying conductive element inside the pot, are the "furniture."
     
    ctmullins likes this.
  11. JohnArnson

    JohnArnson

    May 28, 2019
    A pot is just a viable resistance, and the different types refers to which curve they respectively varies the resistance according to, it's not really rocket science or esoteric magic.

    [​IMG]

    What you see on this graph is that a linear taper surprisingly enough varies the resistance from fully turned down to fully turned up following a linear curve, while one with a logarithmic taper (same as audio taper) follows a logarithmic curve, giving you little difference in the resistance in the first part of the travel from fully turned down to fully turned up, but bigger difference in resistance on the later part of that travel, giving a pot with inverse logarithmic taper will function in reverse of that.

    As said which you use what for on a bass will be totally up to personal preferences.

    Lower resistance pots overall giving you an darker tone and higher resistance pots overall giving you a brighter tone, because a higher resistance will prevent more high frequency content to bleed through to the ground than a lower resistance would (and that way be filtered out of your signal).
     
    Last edited: Jun 15, 2019
  12. I find it necessary to thank all of you who have tried to break through my thick skull and help me understand. Some very smart instructors in the Air Force tried to do the same to no avail. To be honest, the problem I have is not with understanding what is happening but in the nomenclature used to describe it. I understand perfectly what is going on (little microscopic green men running back and forth) but have always been concerned that I may someday describe something wrong and create a huge mess. This particularly concerned me when I was working on bombers going to war. I guess I shouldn't be so worried about it when wiring a bass guitar.

    In any event I have had a breakthrough or an epiphany. Rays of sunshine are beaming down where they did not before. Today I happened upon an add for a 500K pot that described it as having a linear taper and was to be used for volume control. My jaw hit the floor. I am quite sure that the add did not say that yesterday. I started being a little concerned that someone went online and, when I wasn't looking, changed the add. Then I noticed that all of the adds for pots included an audio or a linear designation. I am still finding it hard to believe that I overlooked all of these designations. I am wondering if I am going a little insane. (I'm sure that many people would say I am already there.)

    Could it be that the time I have spent discussing this very issue with TB members has raised my awareness to the point that I am now noticing something that was there all along? Maybe so, but I still have a problem with something being the same but not the same. The add that I saw described the pot as used for volume or for tone but I still will always wonder which is best. No one will ever get me to admit that electronics are anything other than FM. (If you know anything about electronics you will understand.)

    Again, thank you!
     
    Last edited: Jun 15, 2019
    ctmullins likes this.
  13. James Collins

    James Collins

    Mar 25, 2017
    Augusta, GA
    That is a bit of an over simplification of what happens. I know it gets written that way by a lot of people. A resistor doesn't have any preference for frequency. Inductors and capacitors will have variable reactance (sort of like resistance) in alternating current circuits with respect to signal frequency. Resistors treat all frequencies the same. Combined, reactance and resistance is impedance.

    With that said, a lower valued potentiometer can cut some of the brightness back on a signal. The reasons remain shrouded in mystery on the internet.

    I need more time to understand exactly what happens, but I think it has to do more with the way we perceive sound than "high frequencies bleeding to ground."
     
  14. Like I said, It's all FM.
     

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