250K vs. 500K; linear vs. audio taper volume and tone pots?!?

Discussion in 'Just Pickups' started by ZigZag, Aug 3, 2010.

  1. ZigZag

    ZigZag TDPRI Member

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    Hi folks...really need help from you experts!! Tryin' to finish up a tele project with a basswood body, maple neck/rosewood fingerboard, & the following pickup specs. Anybody have suggestions for volume & tone pots?!? ...250K vs. 500K, linear vs. tapered pots?!? I realize that this is very subjective, but suggestions would be REALLY appreciated!!! Thanks EVERYONE!!!
    Pickups: Holding to the vintage specs, the pickups are wound with Formvar not enamel wire.

    "The GVT-1 neck or rhythm pickup is warm, dry and smooth just like the original. Wound with Formvar 43 to get a nice round not muddy tone and a full 7.5K output. Staggered pole pieces, chrome plated brass cover plate and cloth wires maintain the vintage design. You can expect clear natural highs with a great full bodied tight tone giving you a solid rhythm tone.

    The GVT-1 bridge or lead pickup is overwound with #42 Formvar giving it growling vintage tone and hot 9.0K output. Great bottom end punch and powerful mids! Staggered pole pieces at a specific height provides the classic "tele twang" tone. The use of Alnico 5 magnets add to the overall dynamics with a vibrant low end, bright clear highs and just the right amount of "bite"! The pickup is potted in a special ratio of bee and parafin wax to eliminate microphonic noise."

    Please note that the set is calibrated with a RWRP (Reverse Wound Reverse Polarity) for hum cancellation.
     
  2. mechanicdave

    mechanicdave Tele-Holic

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    250K Audio taper is the norm but you can use 500 or 1 meg for increased treble response.
     
  3. jefrs

    jefrs Doctor of Teleocity

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    Formvar is a polyvinyl resin used as insulation on the wire, it is a good insulator.

    The Giovanni GVT are 7k neck and 9k bridge (Giovanni Vintage Tele by Artec)

    So these are somewhat higher wind than usual for tele.

    The volume potentiometer forms the main load to the pickup, its value is chosen to match the impedance of the pickup (which is not the DC resistance). A humbucker, having two coils, prefers a 500k volume pot because it has double the impedance of a single coil, they can sound quite muddy on a lower value. A single coil normally receives a 250k pot, however they are more tolerant of other values, 500k or even 1Meg may be found. The resistance of the pot determines the tuned frequency of the circuit, the higher the value of the pot the brighter it sounds, a lower value sounds smoother. With a high wind single coil or a P90 or a DeArmond then a 500k pot may be preferred. Best to try it and see.

    The usual volume pot on a Fender is logarithmic = audio taper e.g. A250k, this gives a fast cut off, good for swells but is almost silent by '5'. The linear pot is often found on twin humbuckers e.g. B500k, it offers a gradual drop in volume and does not go silent until below '1': for single-coils e.g. B250k. The tonal effect on the pickup is identical given the same value resistance.

    The tone control is a variable resistor not a potentiometer, it is usually 250k irrespective of pickup type, although 300k or even 500k may be found. The typical capacitor may be 22nF (strat/LP) 33nF (some jazzboxes) 47nF (tele). The tone control is always logarithmic/audio taper e.g. A250k. If a high value like A500k is chosen then everything happens around '1', but if a very low value like A100k is chosen then it pulls the top off whilst at '10'. So an A250k effectively takes the cap out of circuit at '10' but gives a usable spread of adjustment from about '5' downwards
     
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  4. blonde52

    blonde52 Tele-Meister

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    Man, this stuff crops up every few days it seems, and its always a different
    answer!
    I thought the LINEAR pot gave the fast cut off and is almost silent by "5".
    The AUDIO taper is the one that offers a gradual drop in volume and does not go silent until below "1".

    Can we get a definitive answer once and for all...Don Mare? Fezz? Someone? Please?
     
  5. blonde52

    blonde52 Tele-Meister

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    Sorry jefrs, that frustration is not directed at you, but my own lack of knowing
    for sure.
     
  6. Tele-phone man

    Tele-phone man Tele-Afflicted

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    In my experience, a linear volume pot goes from silent at "0" to nearly full-on at about "2", and not much change after that. I use audio pots on both volume and tone. For your project, I would suggest 250kA for both.
     
  7. limbe

    limbe Tele-Afflicted

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    I always go to www.fender.com/support choose Wiring/Parts Diagram and try to find the guitar with the pickups most similar to the ones I have.Then I look in the Parts Lists which pots and capacitors Fender have used.
     
  8. Super Locrian

    Super Locrian Tele-Meister

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    Isn't that what all potentiometers are? I'm not an electrician, but here's what it says in Craig Anderton's book Do it yourself projects for guitarists:

     
  9. flyingbanana

    flyingbanana Poster Extraordinaire

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    I can vouch that the audio taper pots definitely drop off more gradually.

    I promise. No more wondering...ok...gotta get back to sleep.
     
  10. Tele-phone man

    Tele-phone man Tele-Afflicted

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    A potentiometer is a variable resistor with 3 terminals being used as a voltage divider, such as when it is used as a volume control. When a pot is being used as a variable resistor, as in a tone control, only two terminals are used, and the control merely changes the resistance between those two terminals.
     
    6stringcowboy and Contrarian like this.
  11. jefrs

    jefrs Doctor of Teleocity

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    Easiest way then is to do it yourself and see, just like wot I did.
    What can I tell you, I'm a professional physicist, I've known this stuff since my early teens a long time ago now.

    Fundamental problem is understanding what logarithmic and linear mean.
    Linear is simple, the resistance changes in a linear manner, a straight line
    Log is more complex, for a start a log pot is not truly logarithmic but three (sometimes four) linear strips laid end to end - that makes these pots jumpy. Log pots are normally pseudo-base10 so they're (supposed to) e.g. 250k at 10 but 25k (one tenth) at halfway 5. A linear pot is 250k at 10 but 125k (half) at 5, and 25k (one tenth) at 1

    If you want to do swell you want the log pot, if you want fine control like I do you use a linear one.
    I set up stage volume with the pot on 5. That allows me to bring it up or down as required without stomping on a pedal.
     
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