Affects of pots and caps on tone

Discussion in 'Tonefreaks' started by Dilver, Apr 2, 2017.

  1. Dilver

    Dilver Senior Member

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    Would changing tone caps (same value/different construction) make a tonal difference when on "10"? Logically, it shouldn't, right?

    Does switching to higher value pots only impact highs/brightness, or could it boost lows as well?

    Does a treble bleed cap affect tone when the tone control is on "10"? Again, to the best of my knowledge and past experience it shouldn't, but maybe I'm hearing things

    I recently changed out reg CTS pots for RS Superpots, and orange drops for PIO caps recently and results were not what I expected. Looking for experience of others...
     
  2. 5F6-A

    5F6-A Senior Member

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    The cap will have an effect even on 10. It is subtle but it's there. Value rather than type or construction is key, in any case.

    Pots might not actually measure what they say.
     
  3. ARandall

    ARandall Senior Member

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    This is a hotly debated area. Mainly as any tonal shift is so subtle that its most likely not to be audible - even with a guitar and amp setup very sensitive to the minute changes in the precise frequencies any change would be present in.

    For most gigging musos you would find none would be able to hear the difference - especially in a band setup.
    A bedroom player might however. Low volume and no other instruments does tend to be the more likely place to hear any change.

    Pots do shift the tone.
    The tone circuit is more linear in the fact you can get a lower value pot simply by turning the knob. A 500k tone pot bleeds less highs on 10, but turn it down to say 6 where it reads 250k to ground and you have a 250k pot on 10.

    Volume pots work in a different way. A higher value too increases top end, but it does this by choking the pickup less. So your entire resonant frequency is further up the register, and has a higher peak. This means you get more of everything generally speaking.
     
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  4. spitfire

    spitfire Senior Member

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    Cap construction is a hotly debated subject. But, as far as I know no one has shown it matters beyond much more than saying "I hear it and that's all the proof I need".

    Lately pot brand has come up. But when it comes to tone, there's no reason to think anything other than value matters. Though different pots will feel different and have different tapers (respond differently when rotated). The extreme being linear vs audio taper.

    You are correct that when a tone knob is set on 10, the cap has the smallest effect. But in most cases, it still has an effect. This is why some people use no load pots. Which just means the tone pot goes to an open circuit (same as infinitely high resistance) and completely removes the tone cap form the circuit.

    The value of the volume pot affects highs and not lows, since it determines the roll off of the higher frequencies.

    Treble bleed is meant to compensate for changes in the volume pot. While I wouldn't say the tone pot and treble bleed are completely independent (nothing really is in a guitar circuit since it is passive), for the most part the tone pot doesn't affect the treble bleed.

    However, since the treble bleed is meant to retain some highs lost when the volume is rolled down, if you roll the tone pot down, the treble bleed become less significant since you're rolling off highs with the tone pot.

    In other words the treble bleed should be most effective when the tone pot is on 10.

    Now, perhaps you meant to say does the treble bleed have an effect when the VOLUME pot is on 10. And in that case it does not.

    If your expectation was a noticeable change when you changed pot and caps (without a significant change in values), I'm not surprised if you didn't hear a difference.

    Again, cap type having an effect is very questionable. If it makes an audible difference, it is at best subtle. Unfortunately there are those that make wild claims that amount to cap type being as significant as pickup changes. Which is clearly absurd.

    Unfortunately when making changes, there are very significant variations in pot and cap values. Values can vary by +-10 % easily and +/-20% is possible. So a 500 K pot could easily be anywhere from 450 K to 550 K.

    Similar or even more so for caps. So the problem when swapping out parts is you could get a value that makes things better or worse and attribute it to the brand of pot or cap material. When in fact, it is simply a value change.

    The guys that are really chasing these effects, will measure actual pot and cap values to know what it is they are really changing. As a result, you sort of need a drawer full of parts to play with.
     
  5. lespauldawg

    lespauldawg Senior Member

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    excellent reply!
     
  6. freefrog

    freefrog Senior Member

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    Discussing if "changing tone caps (same value/different construction) makes a tonal difference" is not only a "hot debated" question: it's a can of worms periodically chewed in endless controversies.

    That said...

    -Yes, IME, changing the component attached to a tone pot makes a "subtle"difference when the pot is on 10. It's not true only for caps but also if the capacitor is swapped/switched for a Q filter/ Tone Qube/ Torres mid Boost and similar LRC circuits.
    FWIW, this difference is measurable with an inductance meter plugged to the output jack of the guitar.
    Obviously, it's more noticeable if the tone pot is a low resistance one.
    But as mentioned above, it won't be perceptible @ gig levels, anyway [I mean: IF the instruments are played altogether in typical gig conditions like a noisy audience, a poor local acoustic and so on. A guitar played loud alone in a silent auditorium would be another story.]

    -no, a treble bleed shoudn't affect anything when the pot is full up, unless there is a residual resistance between center lug and pickup(s) output lug (but even in this case, I don't see how it could make a perceptible difference :hmm:);

    -psychoacoustic illusions are most often mentioned in such cases. Now, IME, there's unseen interactions going on sometimes.
    Example among others : a potentiometer remains a passive electro-mechanical device and not only its measured value may vary but its behaviour when manipulated won't necessarily be consistent.

    I've periodically to test defective tone pots: I've recently seen one of them exhibiting a small (and variable) resistance when set @ zero although it was a brand new CTS pot apparently intact. A few weeks before, I've repaired another one, changed in a no load pot by the action of time on its components. :hmm:

    I've also measured more than once unexpected stray capacitance effects on various components (like the wires used between pickups, pots and switches).

    Although this list is not limitative, such things already explain largely why empirical findings don't always match ideal/theoretical models when it comes to guitar wiring - and please, note that this statement is not supposed to feed a debate, thx. :)
     
  7. HogmanA

    HogmanA Senior Member

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    In my experience, the comments about bedroom volume exposing more differences than stage volume are not true.

    At stage volume, everything is amplified; every part of the guitar sound. It then becomes necessary for the guitarist to use dynamics and sensitivity to control which parts of the sound are loudest, etc.

    Try this at bedroom volume - dynamics in touch don't even register.

    Take it even further - unplug the guitar and most of the players nuances disappear.

    Nuances. this is what it is all about, IME. So much isn't revealed at bedroom volume, and that includes changes to components, and when playing at stage volume, this is when component changes make a difference, especially to guitarists with a fine pallet of nuances.

    It's like telling Michelangelo 'Shut up and paint - red is red'. IME
     
  8. garybaldy

    garybaldy Senior Member

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  9. Freddy G

    Freddy G V.I.P. Member

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    I love this comment and agree 100%
     
  10. freefrog

    freefrog Senior Member

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    Arandall is right: a 500k tone pot rolled back to 250k is strictly the same than a 250k full up.

    A 500k pot used as a volume control, conversely, can't mimic a 250k volume pot.That' what my answer 24 was trying to explain in the topic that you quote. :)
     
  11. 5F6-A

    5F6-A Senior Member

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    Loads of fantastic information posted. That's why I still stick around this forum after 10 years.
     
  12. ARandall

    ARandall Senior Member

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    Not at all. They are talking volume pots for the most part. The bit you have quoted is referring to the tone pot.
    The effect is not at all the same.

    edit - freefrog beat me to it!!
     
  13. GitFiddle

    GitFiddle Premium Member

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    :thumb:

    I've had the same results. I never notice any difference until I am playing at stage volume with a full band. When I joined MLP I had just bought my first real LP, a 99 R7. I loved it. Gigged with it every weekend.

    Some members here convinced me I needed to get rid of those "wimpy" stock caps and put in some real PIOs...
    [​IMG]

    So I ended up replacing the entire harness with a Joney 50s wired harness.
    [​IMG]

    Couldn't really tell any difference at home. Just played it long enough to make sure everything was working correctly. When I took it to the next gig, I could tell a big ole difference and loved the guitar even more. That was some seven years ago. I couldn't tell you whether the caps made any difference or not, since it was a whole new harness and wiring changed from modern to 50s, but the only time I could tell a difference was at full stage volumes.

    Since then, every time a get an LP I'll gig with it fully stock for a few weeks. Each time, I will end up replacing the harness (50s wiring) and sometimes even the pickups before it sounds just right.
     
    Last edited by a moderator: Apr 23, 2017
  14. Jason Taylor

    Jason Taylor Senior Member

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    Awesome!

    Jason
     
    Last edited by a moderator: Apr 23, 2017
  15. Dilver

    Dilver Senior Member

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    Thanks for all the great responses. Something I didn't expect to need to do was readjust the pickup heights after switching to higher value volume pots. I know I'm talking about minute tonal shifts, but I can definitley hear the differences at both bedroom and stage volumes - which is a good thing since removing and reinstalling a wiring harness on a CS-336 is a major PIA!
     
  16. hbucker

    hbucker Senior Member

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    FWIW: Last year I replaced a mini volume pot (the ones Carvin used in the 90's) with a new alpha pot. The guitar's tone improved noticeably with the new pot.

    So, sometimes doing nothing but changing pots with the same value can change your tone. I changed this pot hoping to improve the tone (but mostly because the old one was so stiff to turn, but even I was surprised at how much change there was.
     
  17. spitfire

    spitfire Senior Member

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    This is simply note true. It is the resistance value of the pot that affects tone. While every electronic component has non-ideal behavior, in the case of pots, this occurs at frequencies well above the audio frequencies produced by a guitar.

    While it is possible, if not actual probably that you will hear a difference swapping pots of the same rated value. But this is because they are in fact, not the same value. Pots can be rated with tolerances as high as +/-20 %. So you could be swapping a 500 K -20% = 400 K pot with a 500 K + 20% = 600 K pot. You would certainly hear that difference.

    And much smaller differences should be noticeable as well. The volume pot interacts with the pickup inductance and capacitance, and other circuit capacitance to form a high Q, low-pass filter. While ultimately this causes the high frequencies to drop, at the corner frequency, where the filtering starts to tale significant effect, there is a very pronounced peak in the frequency response.

    The volume pot directly affects the frequency where this peak occurs. This peak is just the same as if you had a peak on an EQ. Changing the pot value is like moving the peak frequency of an EQ.
     
  18. moreles

    moreles Senior Member

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    If "changing pots of the same value" results in a change of tone, it almost certainly means that the actual metered values of the pots -- not the stated values -- are different. One may be on the low side of the % range, and the other on the high side. Happens all the time. With caps, it is my experience that slight differences in real value (as opposed to printed value) are far more significant that composition. I suspect that at least 90% of the time that someone replaces a cheapie cap of a particular printed value with a $ PIO of the same printed value, the real value differences, not the composition, are what contribute to any audible difference. As for volume being the showplace for subtle tonal differences, that's a new one for me and interesting to hear. The problem I have in this situation is that my hearing itself seems to degrade really massively at stage volumes. I think that's true for most people, particularly in band situations. So even if the instrument is displaying its best self when being played at some volume, I'm not sure my ears can really process it in that situation. Catch 22?
     
  19. ARandall

    ARandall Senior Member

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    ^ You do tend to get ear fatigue really quickly at high volume....
     
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  20. 5F6-A

    5F6-A Senior Member

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    I use this 0.02 Centralab cap in my Strat. It reads about 0.016 uF, which is great for positions 2 and 4 (I have a Master tone knob).

    [​IMG]
     

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