Help, please...Volume rolls of too quickly

Discussion in 'Tele Home Depot' started by SwampTwang, Jun 11, 2009.

  1. SwampTwang

    SwampTwang TDPRI Member

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    I just put new CTS 250K audio pots (volume & tone) and Fender Original Vintage pickups in my Peavey Reactor. I wired everything up per the '66 Telecaster pickup wiring diagram from the Seymour Duncan site.

    http://www.seymourduncan.com/support/wiring-diagrams/schematics.php?schematic=66tele

    Problem is, the volume drops off significantly at approximately 8 (if there were numbers) on my volume knob. By 7.5 it sounds like all my other guitars on 2. From about 8 to 0 the volume changes very little, going from "pretty darn quiet" to "none." Tone control rolloff seems to be normal, however. How might I fix this?
     
  2. the_utp

    the_utp Tele-Meister

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    I would wait for at least a second opinion on this, but it sounds like you might have linear taper pots rather than audio taper pots. Linear taper pots bleed the signal to ground based on a linear ratio and don't sound right to us because we hear volume in a logarithmic ratio.

    Linear pots will feel like they have all the change bunched up at one end, though I've more often heard of the problem being the reverse of what you have -- that is, the pot does nothing until you get down to about 3, and then all the drop off happens. So I'm not completely sure that your problem is that the pots are linear. However, components such as pots are mass-produced, so even if you bought ones that were marked "audio taper" they may be linear because a batch got mixed up.

    That's my best guess, but I'd wait for others to chime in before you give up on the pots you've got.
     
  3. maestrovert

    maestrovert Poster Extraordinaire

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    i agree....
     
  4. SwampTwang

    SwampTwang TDPRI Member

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    I thought it was behaving like, well, a reverse linear pot. But I figured if it was marked audio it must be audio. Guess sometimes the factory goofs. I'll have to try a known working audio pot and see if it makes a difference.
     
  5. mgwhit

    mgwhit Tele-Holic

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    You can, of course, test the pot's taper with a multimeter. Set the pot to a mid-way setting, and test DC resistance from the input lug to each of the other lugs. If the values are anywhere close to equal it's linear, otherwise it's audio. You may need to disconnect the pot before you test it, though.
     
  6. cc9cii

    cc9cii Friend of Leo's

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    Maybe you got a lefty pot?
     
  7. Ragtime Dan

    Ragtime Dan Tele-Holic

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    So the problem is the resistance gets high to quickly. I wonder if you could tweak that by putting a 1meg resistor in parallel? I don't know I'm just speculating.
     
  8. SwampTwang

    SwampTwang TDPRI Member

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    Yeah, this will be my first step. Unsolder the pot then put the ol' multimeter on it. Saves me yanking the whole thing out if I don't have to. If it turns out to be a properly working audio pot I'll need to see what I wired incorrectly;)
     
  9. mgwhit

    mgwhit Tele-Holic

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    I don't think there's any such thing as a reverse linear pot. Linear is linear, if you know what I mean. There is a big difference, however, between an audio pot and a reverse audio pot, but I think reverse audio is highly unlikely.

    By the way, my instructions for measuring the side of the pot earlier were rubbish. Center the pot along its rotation and then test resistance from leftmost lug to center. Then test from rightmost lug to center. Linear pots should show both sides as equal. Audio, one side should be 10-30% the other side should be 70-90%. Good luck.
     
    Last edited: Jun 12, 2009
  10. SwampTwang

    SwampTwang TDPRI Member

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    Thanks:)
     
  11. otterhound

    otterhound Poster Extraordinaire

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    I love it . As difficult as it is finding leftie pots , I would doubt that you would get one by mistake . Never know though .
     
  12. spankdplank

    spankdplank Tele-Afflicted

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    Is it possible it is a 1 meg pot, mislabeled? 1 megs with single coils will function almost like an on/off switch if they don't have a treble bleed cap or a bleed cap and resistor wired in the circuit.
     
  13. jefrs

    jefrs Doctor of Teleocity

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    An audio pot, A250k, is the one that bleeds off the sound too quickly, at half way you are down to 1/10 the signal voltage - you want linear volume pots B250k, they allow you to bleed off treble without losing much volume until about a third of the way down. The Linear pot allows fine control of the volume.

    A250k is for the tone control.
     
  14. mgwhit

    mgwhit Tele-Holic

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    This is true of voltage, but not of volume the way the human ear hears it. Linear taper is actually perceived as a hump, and a linear pot would function more like an on/off switch, with most of the volume coming in the earliest part of the rotation.
     
  15. braderrick

    braderrick Tele-Afflicted

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    I agree and I agree. In my limited experience with treble bleed kits I have found that both a cap and a resistor in parallel wil not only retain your highs but also change/smooth the taper of the pot.
     
  16. SwampTwang

    SwampTwang TDPRI Member

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    OK. Problem solved. I removed the pot from the circuit, took measurements with my multimeter, and compared to known working pots. There was nothing wrong with my pot. I compared the wiring diagram from Seymour-Duncan to diagrams from Fender and other sites. I had everything wired correctly. In the end I tried changing the taper of the pot by soldering different value resistors across the legs of the pot. I think I finally settled on a 330k. I also did the "50's mod", connecting the tone pot to the middle lug of the volume pot. Now I have about twice the usable range on my volume control. I notice that the tone control has a pretty big impact on the volume too...rolling off treble also decreases the volume. However, it's not too hard to find some nice usable settings by adjusting both pots. I'm happy. For about $270 I have a US-made, poplar body, maple neck "Tele" (Peavey Reactor) with CTS pots, Mallory 150 cap, and Fender Original Vintage pickups...and it sounds head and shoulders better than the Fender American Standard Telecaster I owned a few years ago.
     
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