Value of this cap?

Discussion in 'Pickup Forum' started by Lonn, Jun 26, 2021.

  1. Lonn

    Lonn Mod Admin Staff Member

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    I think you're expecting me to remember what you said in that other thread days ago, which I didn't.
     
  2. The Tortoise

    The Tortoise Strat-Talk Member

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    Plug your nose with thumb and pointer finger and keep your mouth tightly closed...then blow til your ears pop.
    Boom! Instant treble increase!
     
  3. Dain Bramage

    Dain Bramage Strat-Talker

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    You can try different combos of pots and precision poly/metal film caps, but the pickups can only do so much before you should go a different way.
     
  4. Vermoulian

    Vermoulian Strat-Talker Platinum Supporting Member

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    At risk of kicking a dead horse, here's a higher-level way of looking at a guitar tone circuit and how it works and how different values of components affect the tone.

    The simplest circuit is no circuit: pickup leads go directly to output jack, no pots, no caps, no nothing. This can be an interesting experiment. Notably, this is the brightest your pickup can get. If you run it straight into the amp and it's still too dark for you, get a new pickup.

    The various controls that are added at this point involve sending part of the signal to ground instead of through the amplifier circuit. A volume knob (in a standard Strat circuit, anyway) as it's turned up puts more resistance between the signal and ground, so more of it goes through the amplifier. But (unless you use something like no-load pots) even when the resistance is highest (i.e., the guitar is as "loud" as it can go; the volume is all the way "up") it's not infinite, so some tiny amount of the signal is still going to ground. The higher the value of the pot, the less that gets through. A 500K pot will let less signal leak away than a 250K pot, and a 1 Meg pot less than a 500K pot. This can have a subtle effect on tone. (Note: we're talking about VOLUME pots here.)

    A tone pot is another variable resistor between the signal and ground, but in series with a capacitor. The capacitor means that it does not affect all frequencies---the tone cap lets high frequencies through but blocks low frequencies. The value of the capacitor determines where the cutoff between low and high occurs: the higher the value of the cap, the further down the cutoff frequency goes. So a .047 uf cap will result in more frequencies being affected than a .022 uf cap.

    But the value of the tone pot works here similar to how the volume control works: it determines how much resistance is put in line between the signal (as filtered by the cap) and ground. And again, excepting no-load pots, even with the pot at its limit, i.e., the tone all the way up, there is still a little bit of leakage, because 250K or 500K or 1M is a big number but not infinity. So if you have a standard tone pot in your circuit you are always losing a little bit of your high frequency signal to ground through the pot and cap. More with a lower value pot; less with a higher value pot.

    The difference from value to value can be heard: a circuit with a 1M pot will be noticeably brighter than a circuit with a 250K pot. Check out a Jazzmaster with standard wiring---they came with 1M pots and are very bright, and that's not just the pickups. Or, consider Fender's TBX tone circuit: it's a passive circuit but it gets its treble boost effect is by dialing in an additional 1M of pot value as it is turned up, beyond the standard 250K pot.

    So, if you need more highs out of your guitar, increasing the pot values---volume or tone, but especially tone---will give you more highs, but it can only do so much---as I said, if you run the pickup directly into the amp and it's still not bright enough, there's nothing you can do with a passive circuit to add more highs.

    Another approach is to modify the circuit to have less lows or mids and then turn up the volume, which can get the same effect as boosting treble. Some Rickenbackers had "bright" switches that worked on this principle. That can change the tonal flavor of the guitar, but it's a whole other category of tone modification that is, I think, beyond the scope of what has been discussed in this thread.
     
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  5. StratUp

    StratUp Senior Stratmaster

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    The cap in that case (the .0047 one) is engaged as filter full time in the # 3 position. It's a tone control without an (adjustable, pot) resistor to vary they amount of signal that runs through the cap.
     
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  6. FuncleManson

    FuncleManson Strat-Talk Member

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    Thanks. Like I said, some of this stuff is over my head. I was just wondering why the cap affected the tone in that instance.
     
  7. mazzolar59

    mazzolar59 Strat-Talker Silver Member

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    Check the impedance of the pots. Fenders come with 250k pots but, they could be lower. You could use 300k pots but I wouldn’t go any higher.
     
  8. Chipss36

    Chipss36 Strat-O-Master

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    I measure each pot, the tolerance of pots is pretty bad.

    pretty much measure and mark every pot, with its measured value.

    generally, I find higher values more useful , so I pay for the higher value pots as measured. Rather than sort em myself. And have low value pots I can not use. Some are way way off in value.

    300ohms ish on sc , and 550 and up on hb…works 90% of the time.

    gibson is real bad about using lower values, they sound like a blanket is on the amp to me.
    A pot value change works wonders.

    done this to about 20 modern Gibsons, with people happy with the outcome.
     
  9. AngelDeVille

    AngelDeVille Senior Stratmaster

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  10. AngelDeVille

    AngelDeVille Senior Stratmaster

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  11. fezz parka

    fezz parka fezz parka

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    On the nose Ryan.

    You can brighten it by doing the Gibson/Ted Greene/some-call-it the fezz parka mod.

    You move one wire.

    [​IMG]
     
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  12. JB74

    JB74 Senior Stratmaster

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    Amen. one wire mod.
     
  13. Wound_Up

    Wound_Up CUSTOM USER TITLE Silver Member

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    Nope. Not at all.
     
  14. HazyPurple

    HazyPurple Without stress... my life would be empty Silver Member

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    So the term Direct Current Resistance, with regards to pups, is BS?
     
  15. Antigua

    Antigua Senior Stratmaster

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    Actually you can use an inductor in place of a cap and get this effect, but it has to be a high Q inductor, such as a Bill Lawrence Q Filter.


    If you disconnect the cap, the tone circuit is open, and the 250k pot resistance no longer matters, sort of a like a no-load tone pot scenario. It's often so subtle that you might not notice, especially with a pickups that has a lot of steel parts that obliterate the Q factor to begin with. No-load pots make most of a difference when a pickup has a high Q factor that would be audible if not for the loading.

    Technically, there's a value at which the cap appears to "open", or disconnected, some value below 1nF, so small that nobody would ever use it as a tone cap.
     
    Last edited: Jul 8, 2021
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  16. Antigua

    Antigua Senior Stratmaster

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    I ordered a set of Deluxe Drive pickups, but haven't measured them yet. Assuming they have an inductance of 5 henries, the resonant peak would be lower, but the Seymour Duncan SSL-5 has an inductance of 7 henries, so they're still not as wound as that. Subjectively, you can turn the treble up on the amp as you might have to for a humbucker loaded guitar, and the pickups will still sound bright all the same, but to suggest that 5H pickups are similar to Tele pickups is disingenuous on Fender's part. There's no magic going on that lets them defy the physics. It's not physically possible that they're going to exceed the 57/62's in terms of audible brilliance, nor most of rest of their pickup line, for that matter. I'm not sure if the inductance is really 5H though, I'll find out. They sounded pretty bright in YouTube demos, but where there's a will there's a way.
     
    Last edited: Jul 8, 2021