what does this resistor do in this diagram

Discussion in 'Just Pickups' started by hopdybob, May 21, 2019.

  1. hopdybob

    hopdybob Tele-Holic

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  2. trev333

    trev333 Telefied Ad Free Member

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    I'm thinking it's a filter to take a certain frequency out of every position.... treble maybe?... different values of resistor would have different effects....

    I'm sure someone with more ideas will chime in soon..:)
     
  3. Asmith

    Asmith Friend of Leo's

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    Wouldnt do a lot, it would just counteract the the slightly higher than normal volume pot value bringing the load down to 275k plus the tone pots' effect. It'll have more effect if you roll the volume off but I still doubt its effectiveness, your cable will have a bigger impact on your tone.
     
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  4. kbold

    kbold Tele-Meister Silver Supporter

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    Agree. Pretty much does nothing.
     
  5. Teleterr

    Teleterr Friend of Leo's

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    It changes the value of the pot, probably for sweet spot loading. I use a 500K V pot for singles then turn down to where the p-up sounds best, were the load gives the contour I like.

    Asmith are you sure ? I think that it works backwards from what you stated.Small values in parallel w big values stay close to the small value. Big values in parallel will change by a greater %.
     
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  6. warrent

    warrent Friend of Leo's

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    It does two things, at full volume it reduces the resistance of the pot to 275K if the 300k is accurate. It also changes the pot's taper slightly. In the end it might make the pickups less bright. (but it would be hard to hear)
     
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  7. memorex

    memorex Friend of Leo's

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    It's there to mock you.
     
  8. Teleterr

    Teleterr Friend of Leo's

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    I think it would be easy to hear. W a single and a 500 K theres definitely a sweet spot where the bass comes on strong and the treble is "natural". More resistance, and the treble SEEMS unaturally emphasised. I think its tuned for that p-ups spot. Its not smack in the face obvious, but definitely there.
     
  9. Asmith

    Asmith Friend of Leo's

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    Resistance in parallel is equal to the the reciprocal of the sum of the reciprocal of the resistances in parallel.

    Or

    275k=1/((1/300k)+(1/3300k))
     
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  10. Asmith

    Asmith Friend of Leo's

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    The resistor drops the equivelant potentiometer value by 25k thats less than 10% of 300k. A potentiometer has a tolerance of +-20% so that 300k pot could actually measure anywhere between 240k and 360k so that 25k is pretty meaningless in the grand scheme of things and can easily be lost in the variance of the components.
     
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  11. Teleterr

    Teleterr Friend of Leo's

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    I was pointing out that you'd hear the difference more on full vs barely on instead of vs versa.
    But I don t think its there for contour change so much as it is to bring out the best p-up tone. Giving the load it "wants".
     
  12. Digital Larry

    Digital Larry Tele-Afflicted

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    I'll add my vote to the "skeptical it does anything useful" column.
     
  13. Asmith

    Asmith Friend of Leo's

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    If it was about getting the right load for the pup then it would make more sense to use a 1Meg potentiometer and a 390k resitor in place of the 3Meg3 resistor. You'd get a load between 260 and 295 depedning on the tolerance of the potentiometer (resistors can be had at a negligible less than 1% tolerance). The current setup means the load can be anywhere between 220k 325k.
     
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  14. warrent

    warrent Friend of Leo's

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    If I was to hazard a guess as to why it's there two things come to mind. One it's probably easier to source close tolerance 300k pots at production volume versus 275K. Second it looks special. It looks like John and Paul spent months agonizing over the resistor value to get the right tone.
    If you can hear the difference in a 25K value for a pot once you take into consideration all the variable tolerances from the pickups down to the guitar cable I salute you. I couldn't.
     
    Last edited: May 21, 2019
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  15. rigatele

    rigatele Tele-Afflicted

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    What is really amazing is that it is said to replace a 2.7M resistor on the prototype (see the web link). I'm too lazy to do the math right now, but I think that difference means an effective difference in the pot value of only a few kilo-ohms. This is nonsense, there is no way such a tiny change could make the guitar "brighter" as stated. Not enough to hear, anyway.
     
  16. hopdybob

    hopdybob Tele-Holic

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    its good to see/read that i am not the only one that has questions about this 'tweak' :rolleyes:
     
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  17. Teleterr

    Teleterr Friend of Leo's

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    Hook up a single to just a 500 K pot CENTER lug so the loading changes. There will be a point were 10,000 ohms + or - makes a difference in Tone , but not volume. I ve done this, so its not my theory, but my direct experience. It is subtle so most won t care , but John apparently does.
     
  18. Teleterr

    Teleterr Friend of Leo's

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    300-400 K is where the sweet spot is for most 6K dc Strat singles, so it could be set for: optimum most open sound to a little darker, ignoring the more resistance extra "unatural" brightness possibility.
     
  19. Dennyf

    Dennyf Tele-Afflicted

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    It adds guitar-geek appeal. Carbon film is just icing on the cake.
     
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  20. warrent

    warrent Friend of Leo's

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    Why do you keep mentioning 500K pots? The circuit uses 300K pots. The difference between 500K and 250K is audible but this is not what we are talking about.

    But the resistor lowers the value below 300k so that's out of your sweet spot.
     
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