What happened to my volume pot?

Discussion in 'Luthier's Guitar & Bass Technical Discussion' started by kftplay, Dec 24, 2009.


  1. kftplay

    kftplay Member

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    Dec 19, 2009
    I had active electronics in my Strat and recently removed them and went back with 2 new SD/SS1 sgl coils and 1 SD Lil' 59' in the bridge. Dropped a blender in the #2 tone pot, and new tone and volume pots. Now and instead of a nice clean increase decrease with the volume pot it's offensively thin and "middy" 0 to 8. From 8 to 10 the sound is distorted and uncontrollably so. Replaced the volume pot with another, now 0 - 2 not signal, 2 to 4 full volume, 4 to 10 no change what so ever. What am I missing
     
  2. KGWagner

    KGWagner Member

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    Sounds like the pot you put in is a linear taper vs. audio taper part. You want the audio taper.

    The human ear doesn't perceive changes in loudness in a linear fashion. It's a logarithmic scale. You need a factor of 10 change to hear a doubling in apparent volume. So, control changes can't be linear or you'll hear all the change in a short throw at one end, and little or no change for the balance of the throw.

    This plot contrasts linear vs. log response curves...

    [​IMG]

    The red and blue lines are the log curves, and the green is linear. If this plotted apparent volume, what you hear with a linear pot looks like the log curves, while what you'd hear with an audio pot looks like the linear (green) plot.

    I know, it's not intuitive, but that's humans for you <grin>
     
  3. David Collins

    David Collins Member

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    Linear or audio pots work fine for volume - search the archives for thorough discussions on this. They each can work a bit different, but neither should result in the descriptions you provided. For example, no volume pot itself will cause the guitar to sound distorted. What pots are you using, and how are you wiring it? Something sounds fishy....
     
  4. KGWagner

    KGWagner Member

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    No pot will cause distortion, but a large, rapid change in a few degrees rotation to a small change in the balance of the rotation is certainly a taper issue. There's no question about it. If we knew the part number of the pot, we'd know for sure, but I'm 99% confident here.

    What kind of output the pickup produces and how the amplifier responds to it is another issue.
     

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