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Reducing 250k value

Discussion in 'Tele-Technical' started by RockinCarl, Oct 12, 2011.

  1. RockinCarl

    RockinCarl Tele-Afflicted

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    I'm using a blender pot instead of a tone control in one of my Teles. Without the tone control, the Tele is just a bit too bright. I'd like to add a resistor to the volume pot so it "sees" the same load it would if I had a 250k tone control... Would that mean I'd connect a 250k resistor to the 1st and 3rd lugs on the volume?

    Thank you!
     
  2. dsutton24

    dsutton24 Doctor of Teleocity Ad Free Member

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    It's not a matter of loading alone, you need to roll off some highs. Connect a .022µf capacitor to the volume pot as per usual, and connect the other lead of the cap to one lead of a 250K resistor. Connect the other lead of the resistor to ground.

    You'll find 220K, 270K, 330K are readily available values. Higher resistance means less treble loss.
     
  3. RockinCarl

    RockinCarl Tele-Afflicted

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    Thank you! I read this trick long ago, and couldn't remember it at all. So the one that would sound the most 'natural' would be a 220k cap, if I'm used to the sound of two 250ks?
     
  4. David Collins

    David Collins Tele-Afflicted

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    Actually I would say that yes, putting a 250k resistance load across lugs 1 and 3 will have the exact same result as having a tone pot locked at 10. Including a cap in series with this resistor may be a more correct simulation in the abstract, but in all practicality it would not make for any audible difference.
     
  5. Wayne Alexander

    Wayne Alexander Friend of Leo's Silver Supporter

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    Pots are cheap. Why not just replace the pot with a lower value?
     
  6. dsutton24

    dsutton24 Doctor of Teleocity Ad Free Member

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    Huh?

    If you put a 250K resistor across a 250K pot it would yield a max resistance of 125K, Still well over ten times the 7K or so resistance of the typical pickup, so it's not going to make much of a differance in the sound. If anything the combination of the relatively large inductance of the pickup and the relatively lower resistance will roll more lows off, and aggravate the trebly nature of the guitar.

    The cap is there to roll off highs, the 220K resistor is there to simulate a pot set for full resistance. The values of either component can be tweaked to get the sound desired.

    Hey, it's easier to test this stuff on a telecaster than any other instrument I can think of. That seperate control plate is an experimenter's dream.
     
  7. KokoTele

    KokoTele Doctor of Teleocity Vendor Member

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    That's what you get when you put the resistor across lugs 1 and 2. David's solution puts them across lugs 1 and 3, 3 being the ground lug.
     
  8. dsutton24

    dsutton24 Doctor of Teleocity Ad Free Member

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    Nah. If you put a 250K resistor across lugs 1 and 2, you'll get a pot with something approaching 125K min and 250K max with a weird taper from lug 3 to ground (overall loading) and 0 to 250K from lug 2 to ground, again with a weird taper. If you put a 250K resistor across lugs 1 and 3 you'll get 125K max with a less weird taper.
     
  9. David Collins

    David Collins Tele-Afflicted

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    In the perfect theoretical form, putting a 250k resistor in series with a cap across lugs 1 and 3 would be the exact equivalent of a tone pot wired standard and locked at 10, which appears to be what Carl was looking for.

    With the tone on 10 however, the cap is not a limiting factor close to any of the frequencies effected by the loading of the pot resistance. In other words, with the tone on 10, the capacitor can be shorted across without any change in signal. Therefore, if you were going to use a fixed resistor to simulate the tone on 10, there would be no need to use a cap at all. Just wire a 250k resistor between the outer lugs, or switch output to ground (same thing), and you have a volume control that will act the same anywhere throughout it's range as though there were a tone pot locked on 10.

    If you want it purely and technically correct then you could run a cap in series with the resistor. I just don't believe anyone would be able to hear a difference between that or the resistor alone in a blind test.
     
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