Know lots about potentiometers

Discussion in 'Pickups, Electronics & General Tech' started by noodles, Feb 16, 2007.

  1. noodles

    noodles Contributor

    Messages:
    18,493
    Likes Received:
    2,335
    Joined:
    Aug 23, 2005
    Location:
    Woodbridge, VA
    What is the difference between 250K & 500K pots?

    Either 250K or 500K pots can be used with any passive pickups however the pot values will affect tone slightly. The rule is: Using higher value pots (500K) will give the guitar a brighter sound and lower value pots (250K) will give the guitar a slightly warmer sound. This is because higher value pots put less of a load on the pickups which prevents treble frequencies from "bleeding" to ground through the pot and being lost. For this reason, guitars with humbuckers like Les Pauls use 500K pots to retain more highs for a slightly brighter tone and guitars with single coils like Stratocasters and Telecasters use 250K pots to add some warmth by slightly reducing the highs. You can also fine tune the sound by changing the pot values regardless of what pot value the guitar originally had.

    What is the difference between Audio and Linear taper pots?

    Audio and Linear taper pots have the same total resistance but differ in which position of rotation the pot will reach the 50% value. Linear pots are usually marked with a B or Lin (examples 250KB, B250K, 250K Lin) and will reach 50% of its total resistance in the 50% rotation point. Audio taper pots are usually marked with an A or Aud (examples 500KA, A500K 500K Aud) and will decrease most of the resistance in the last 50% of the rotation. This can give a more gradual audio reduction is some cases. Most manufactures and builders either use Audio taper pots for volume and tone or linear for volume and audio for tone. However, if a problem of exists where a volume or tone pot has no effect on the sound, try a changing the taper. How to check the taper with an ohm meter: Set the pot to the center position (50% rotation) and measure the resistance between the center pin and each of the outer pins. If the the resistance is equal (50% of the pots value) the pot is linear. If the values are not equal, the pot is an Audio taper.

    What is a Fender TBX tone control and how does it work?

    Some Fender guitars come equipped with a special pot called a TBX Tone Control T (treble) B (bass) X (Cut) that cuts either treble or bass instead of a tone pot that cuts treble frequencies only. This is done with a ganged 500K-1M ohm control pot that is wired to work as a low-pass filter in one direction and a high-pass filter in the opposite direction. A center detent in the middle position is provided for the off or "flat" position. Although Fender altered their Start tone configuration to have the TBX control the middle and bridge pickups, it can be also be wired as a master treble/bass control. The TBX can also be used in place of any standard tone control on any guitar.

    What is a Fender No Load tone control and how does it work?

    The Fender No Load Pot is used on some USA Strats, Teles and Fender basses and is wired like a standard tone control. From settings 1-9 it works like a standard tone then clicks in at 10 (full clockwise/ bright setting) and removes the pot and capacitor from the circuit. This eliminates the path to ground that exists with standard pots even in the full treble position. By eliminating the path to ground thru the pot, the only load on the pickup is the volume pot. So if 250K pots are used, the load is reduced from 125K to 250K and if 500K pots are used, the load is reduced from 250K to 500K (high resistance = low load) The reduced load allows more power output from he pickup and reduces the amount of high frequencies that bleed off to ground. This gives a noticeable increase in brightness and output in the full treble setting. The no load pot can be used in place of any standard tone control on any guitar or bass.
    How does the tone capacitor value affect the sound of the guitar?

    Most guitars and basses with passive pickups use between .01 and .1MFD (Microfarad) tone capacitors with .02 (or .022) and .05 (or .047) being the most common choices. The capacitor and tone pot are wired together to provide a variable low pass filter. This means when the filter is engaged (tone pot is turned) only the low frequencies pass to the output jack and the high frequencies are grounded out (cut) In this application, the capacitor value determines the "cutoff frequency" of the filter and the position of the tone pot determines how much the highs (everything above the cutoff frequency) will be reduced. So the rule is: Larger capacitors will have lower cutoff frequency and sound darker in the bass setting because a wider range of frequencies is being reduced. Smaller capacitors will have a higher cutoff frequency and sound brighter in the bass setting because only the ultra high frequencies are cut. For this reason, dark sounding guitars like Les Pauls with humbuckers typically use .02MFD (or .022MFD) capacitors to cut off less of the highs and guitars like Strats and Teles with single coils typically use .05MFD capacitors to allow more treble to be rolled off. Keep in mind that the capacitor value only affects the sound when the tone control is being used (pot in the bass setting) The tone capacitor value will have little to no effect on the sound when the tone pot is in the treble setting.

    Does the number of control pots used affect the sound?

    Yes: Since the load on the pickups is determined by the total parallel resistance of all pots that are being used at a atime, using fewer pots will reduce the overall load and give a slightly brighter sound. Also, connecting more pots is the same as using lower value pots, two 500K pots will loose or "bleed" the same amount of treble frequencies as one 250K pot. To lessen the effect, switching should be designed (when possible ) to remove pots from the circuit when the related pickup is not selected. An example of this is the Les Paul: bridge controls are out of the circuit when in the selector is in the neck position and the neck controls are out of the circuit when the selector is in the bridge position.

    Pickup and Switch FAQs

    What is the difference between single & four wire humbuckers?

    Single wire humbuckers, (also called single conductor) have the link between the two individual coils hard wired together internally. They also have one coil lead hard wired to ground. This means the pickup can not be coil split, reverse phased or switched to parallel. These pickups usually have a metal braided coaxial output wire. (braid=ground and the center wire=hot) Four wire humbuckers have both wires from each coil plus a ground wire (usually bare wire) all in one cabel to allow thw cois to be split, reverse phase or switched to parallel with custom and optional switching. For standard humbucker wiring (series-in phase) two of the wires (series link/ coil tap wires) are connected together and the remaining two wires are used as hot and ground. (the wire used as the ground is combined with the bare ground wire and soldered to the back of the volume pot or other ground spot. The wire used as hot is soldered to the pickup switch or volume pot.
    What are the differences between coil tap, series/parallel & reverse phase?

    With a single 4 wire humbucker, there are six possible modes.

    1. Series-In Phase This is the standard humbucker wiring. Maximum power output with strong bass and smooth attack. (hum canceling)
    2. Single Coil (South) Just the South coil of the pickup alone. Good traditional single coil tone with a sharper attack. (not hum canceling) Use in combination (series or parallel) humbucker in "North coil mode" or a standard single coil (north) for a hum canceling Strat/ P.R.S. style tone.
    3. Single Coil (North) Just north coil of the pickup alone. Almost the same tone as the south coil but slightly different due to its different position. (not hum canceling) Use in combination (series or parallel) with another humbucker in "South coil mode" or a standard single coil (South) for a hum canceling Strat/P.R.S. style of tone.
    4. Parallel-In Phase Great single coil style tone with no hum. Best option for clean, bright tone without the noise of standard single coil wiring. Strong treble with crisp attack but lower power output. (hum canceling)
    5. Series-Out of Phase Thin "phased" sound with good power. Great for funk. (not hum canceling)
    6. Parallel-Out of Phase Thinner "phased" sound with low power. (not hum canceling)

    Original source: Potentiometers FAQ at GuitarElectronics.com
     
  2. ohio_eric

    ohio_eric Contributor

    Messages:
    9,224
    Likes Received:
    1,225
    Joined:
    Feb 18, 2006
    Location:
    Ohio
    Guitar Electronics.com is a good resource in general. That's a good link. :yesway:
     
  3. JPMDan

    JPMDan IT'S OVER 9000!!!! Contributor

    Messages:
    7,075
    Likes Received:
    417
    Joined:
    Jun 4, 2006
    Location:
    New Orleans, Louisiana
    so 500k pot is better for volume, audio or linear? I'm looking to order 2 new pots for my ESP.
     
  4. SeanC

    SeanC loves metal

    Messages:
    702
    Likes Received:
    193
    Joined:
    Nov 9, 2006
    Location:
    Oregon
    For an X2N would it be overkill to use a 500k pot? Or is it better to use a 250k?
     
  5. D-EJ915

    D-EJ915 Forum MVP

    Messages:
    34,865
    Likes Received:
    1,461
    Joined:
    Oct 1, 2005
    Location:
    USA
    I use a 500k with mine and it sounds awesome, remember that a 250k pot is just a 500k turned down a little bit.
     
  6. MF_Kitten

    MF_Kitten Set up us the bomb

    Messages:
    11,332
    Likes Received:
    1,770
    Joined:
    Apr 21, 2007
    Location:
    Kopervik, Norway
    does that mean that you can change the K value of a pot?
     
  7. BigM555

    BigM555 I SS.org Salute You! Contributor

    Messages:
    1,728
    Likes Received:
    192
    Joined:
    Dec 16, 2006
    Location:
    Ontario, Canada
    I ran across that link myself not too long ago.

    Great one! :yesway:
     
  8. TomAwesome

    TomAwesome I LIKE JUICE!!!

    Messages:
    10,137
    Likes Received:
    574
    Joined:
    Mar 1, 2007
    Location:
    Texas
    Great info!
     
  9. lostcomingdown

    lostcomingdown SS.org Regular

    Messages:
    64
    Likes Received:
    8
    Joined:
    Sep 23, 2007
    Location:
    st. petersburg, FL
    @mfkitten:

    no, you can't change the K rating of a pot. well. kinda. see, variable resistance is kinda what pots do. it's a variable resistor soldered into place between the hot wire and ground points, and depending on where it's set, it bleeds off a little bit of your signal/all of your signal to ground, which makes for 0 potential between ground and input, which makes for no potential difference at the amplifier input, and no sound output. with the signal your guitar's putting out being so small, from a design standpoint, there's no difference between a 250, 500, and 1M pot, but um. they sound different, like the other guy said. sorta. someone kick me if i'm wrong, it's been known to happen.
     
  10. Quicksilver689

    Quicksilver689 Jesus freak

    Messages:
    205
    Likes Received:
    4
    Joined:
    Sep 27, 2007
    Location:
    Martinsburg, WV
    nice link - thx for sharing!:hbang: :shred: :agreed:
     
  11. Ultramog

    Ultramog SS.org Regular

    Messages:
    16
    Likes Received:
    2
    Joined:
    Jul 27, 2007
    Location:
    North Jersey
    Thanks for posting this. It helps as I spend waaay too much time drawing & redrawing pickup selector diagrams at work.

    Is there a No Load Volume Pot? Sounds like a dumb question, but here's what I'm after: 3-way toggle (Single Coils in Series, 2 Humbuckers, Single Coils in Parallel) plus 2 volumes. But I want to be able to get take individual pickups out of the circuit when volume is completely off.
     
  12. MaKo´s Tethan

    MaKo´s Tethan SS.org Regular

    Messages:
    1,875
    Likes Received:
    751
    Joined:
    Apr 13, 2009
    Location:
    Argentina
  13. Miss D Corona

    Miss D Corona SS.org Regular

    Messages:
    161
    Likes Received:
    1
    Joined:
    Jul 17, 2010
    Location:
    Ireland
    You should change the title from 'potentiometers' to 'pots' ;)
     
  14. Hasmamagee

    Hasmamagee SS.org Regular

    Messages:
    41
    Likes Received:
    2
    Joined:
    Aug 17, 2010
    Location:
    Bloomfield Hills, MI
    Hey everybody I put a thread in earlier about a wiring diagram for a guitar with 3 humbuckers 3 tone pots and 3 volume pots so far no one has commented but maybe one of you guys know some help would be seriously appreciated
     
  15. JonnyDeath

    JonnyDeath SS.org Regular

    Messages:
    25
    Likes Received:
    2
    Joined:
    Dec 13, 2010
    Location:
    Cleveland
    In a sense, yes.
    You can add a fixed value resistor in either series or parallel but ultimately no matter how you change the perceived value, you can't make a 250K pot function like a 500 K or 1 meg, only vice versa.
     
  16. filipe200x

    filipe200x Custom is better

    Messages:
    112
    Likes Received:
    23
    Joined:
    Sep 16, 2007
    Location:
    Big River, South Pole
    I have a 7 string with two humbuckers. I'd like to install a fender no load, would that be ok with this pot being a 250k? Also if not, does the fender TBX turns off at the center positions allowing the same amount of highs as if it had no pot, or does it just work like a regular pot on 10?
     
  17. Scookers

    Scookers SS.org Regular

    Messages:
    22
    Likes Received:
    4
    Joined:
    Nov 10, 2010
    Location:
    Menominee, MI
    I used Fender No-Loads on my Rogue 7-string Frankenstein. There is a modification to use the Fender No-Load as a volume pot. They are 250K pots and they work. The only problem is when you turn the thing down to 0, it still lets some signal through. A noise gate fixes this pretty well. I also used a .002 uF capacitor in the tone circuit. It also has a Dimarzio Evolution 7 at the bridge. It's hot as hell. There is a special way to wire this thing up as a volume pot. I screwed it up at first and brought it to a guitar shop where some guy took all of my work and screwed it right the hell up. Then he told me it couldn't be done. This made me bound and determined to find the fuck up and make it work. I looked at the diagram again and said, "Duh!" It works great now. I might have to tear apart my guitar and make up the diagram. It's been years since I did it. Anyway, the downside is the volume not turning down all the way. The upside is a hot as hell guitar. Was I super impressed with it? Not really. Otherwise I would have done it to all of my guitars. Try it out and see if you like it. I just know that particular guitar is crazy hot. Let me know if you need the diagram. I'll make it for ya. I found it on guitarnuts.com, but can't find it there anymore.
     
  18. yingmin

    yingmin Parker über alles

    Messages:
    4,588
    Likes Received:
    444
    Joined:
    Jan 27, 2009
    Location:
    Tacoma, WA
    Can someone explain to me why this works the way it does? I've been asking around, and even my guitar tech, who is otherwise never without an answer for things like this, couldn't explain it to me. It seems to me like it should be the opposite: since 500K pots have higher impedance, wouldn't they be putting more resistance on the signal? Conversely, using 25K pots like for EMGs with passive pickups totally chokes the tone, but by my way of thinking, it should let the most signal through. What am I missing? I'm not amazingly knowledgeable about electronics, so there's obviously something about this I'm misunderstanding, but can anybody tell me what?
     
  19. SD83

    SD83 SS.org Regular

    Messages:
    1,235
    Likes Received:
    78
    Joined:
    Sep 19, 2009
    Location:
    Münster, Germany
    I'd like to hear the answer as well, as I have the same trouble understanding it.
     
  20. veggie7sXe

    veggie7sXe SS.org Regular

    Messages:
    18
    Likes Received:
    15
    Joined:
    Jun 16, 2011
    Location:
    Greeneville, TN
    Active pickups are wound to be low outputs. But i guess with the battery juice it makes them spit out over 500 ohms of aggression.
     

Share This Page