Know lots about potentiometers

Discussion in 'Pickups, Electronics & General Tech' started by noodles, Feb 16, 2007.

  1. Racerdeth

    Racerdeth SS.org Regular

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    I could be wrong but I think it's resistance between the signal and ground rather than the signal and hot, so when the vol's turned up full you have the full 500k resisting the signal going to ground, but if you had a 250 you'd only have 250k of resistance between ground, so more of your signal bleeds off. I'd appreciate someone to confirm this though.
     
  2. Racerdeth

    Racerdeth SS.org Regular

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  3. brutalslam

    brutalslam SLAMZ

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  4. whosdealin

    whosdealin SS.org Regular

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    Great thread.... Maybe we can talk a bit about capacitors also. I havent experimented much with them and was wondering if anyone can share there experiences of trying different types, values.....and what the change in tone was. Thanks !
     
  5. guitarneeraj

    guitarneeraj WindMarp Contributor

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    Basically, your guitar's pickup(s), the volume pot, tone pot, tone capacitor, and cable impedance form one RLC network, in essence a resonant low-pass filter of 2nd order to be precise.

    If you're still with me, following is the circuit diagram for a pickup's equivalent circuit and the external load which consists of(all not shown) volume pot, tone pot, tone capacitor and cable impedance.

    [​IMG]

    And here is how a resonant low pass filter looks like :

    [​IMG]

    Changing the value of any of the components in this RLC network will affect the tone i.e. output of the instrument.

    The tone pot affects the frequency axis, while the volume pot affects the boost/cut around the center frequency.

    With me so far?

    Now, the higher the value of the tone and volume pots, the more the high end roll-off (steepness of the filter beyond cutoff frequency). Wikipedia has a good article on filter roll-off, if you're more interested further in the mathematical part of it. Roll-off - Wikipedia, the free encyclopedia

    Also, just my :2c: this guy has excellent demos:
     
  6. oliviergus

    oliviergus Djentiver Gustafsson

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    Where can I get a "slow" pot in europe? The pot I have in my ibanez atm is too easy to turn.
     
  7. Cannibalbritney

    Cannibalbritney SS.org Regular

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    In all my frankentstrats I have one humbucker *bridge* and I wire my pickups direct to the output jack... no pots... maybe an on off switch... but i like it direct. I mean in most cases you have a tuner or a bypass pedal on your rig anyway... so just stomp it to remove noise... but in my opinion it sounds MUCH better, you get the full sound of what the pickup is trying to do... I mean EVH has been doing that for years, among many other major shredders... there has to be a good reason for it :-D
     
  8. DropDizzle

    DropDizzle SS.org Regular

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    Is there a difference between a 250k ALPHA pot and a 250k CTS pot?
     
  9. maxz

    maxz SS.org Regular

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    no you cant change the ohms value/just change the pot to higher value . unhook um use a kill switch total output total tone/get rid of tone too. too get higher value with existing pots wire vol.&tone(make into a 2nd a vol.) in series more volume!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
     
  10. maxz

    maxz SS.org Regular

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    try 1meg pots if u have to hav a vol. they have 2meg now even better/unhook the tone 4 more output-or turn it into another vol.run in series more gain. i do use pots;2 cut either coil on a humbucker pu most always the neck pu 3 difnt sounds 1 pu!
    it takes 2 pots or more to work- if your good youll figure it out~!
     
  11. guitarneeraj

    guitarneeraj WindMarp Contributor

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    How does changing say, a 250K pot to 500K give more volume??! You're stating something wrong, my friend. The output from your pickup will always remain constant, you cannot increase it unless with some active circuit elements. So if you wire 2 pots in series, you have more resistance to ground and so the volume will of course decrease. Imagine the 500K pot as being two 250K pots. Hence, a 500K pot, in comparison to 250K, would mean that beyond 250Kohm resistance on the 500K pot (i.e. max position on the 250k) , you get an added 250K resistance to ground, which is (partly) what prevents high frequencies from getting lost; and also why you get more attenuation on your signal, than when using a 250K pot.

    In essence, a "volume" pot (passive) is not like a "gain" control, it's more like an attenuation control. At Volume = max, you get the full output from the pickup, as you roll it down, the output gets attenuated because some current from the pickup's output is drawn by the resistance of the potentiometer.

    This is a dubious statement my friend. Potentiometers are after all resistors, only variable. Therefore, same laws which apply for resistors, also apply for potentiometers. If you have higher value pots, they will be noisy like a futhermocker. This is because, the higher the resistance, the more the thermal noise.

    However, I do agree that the tone pots on guitars are pretty useless with the stock ceramic disc capacitors that are put in there. Anyone wanting to get a richer and more intuitive control should definitely think about firstly replacing the tone pot with an Audio (logarithmic) Taper potentiometer, and then experimenting with different types (yes, types) of capacitors. A 0.047uF ceramic capacitor will sound vastly different from a Sprague orange drop, in a tone control. Please refer the previous YT link I posted for demos from the same guy about how different types of capacitors sound.

    I really hope this thread does not spread misinformation. If you have any doubts about pots, don't hesitate to ask!! I'm sure there are a lot of knowledgeable people on ss.org who will be willing to answer!
     
  12. guitarneeraj

    guitarneeraj WindMarp Contributor

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    Only in the quality!! :)
     
  13. DropDizzle

    DropDizzle SS.org Regular

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    care to explain to a newb? ^^
     
  14. guitarneeraj

    guitarneeraj WindMarp Contributor

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    Okay, for example, let's take the CTS 450 Series pots (i.e. the standard ones which are available on eBay/AllParts), and ALPHA 16mm pots.

    The minimum tolerance for CTS pots can be upto +/-10%, whereas for ALPHA pots, it is +/-20% by default. Of course as the tolerance decreases the price of the part will increase, since we're talking precision here. To be noted is that cheapest CTS pots have, by default +/-30% tolerance. The tolerance is basically, the variation in the total resistance of the pot. So if you buy a 250K pot, it will never show exactly 250.0K ohm, on a multimeter. The tolerance means that the resistance value can vary anywhere between +/- X% of the specified value.
    So.... for 250K with 10% tolerance, the actual value can be anywhere between 225K to 275K, but with 20% tolerance, the actual value can be anywhere between 200K to 300K!!!

    With CTS pots, the power rating is also better than ALPHA. Another point to consider, is the robustness. In my opinion, CTS pots are better in terms of manufacturing quality. You might also want to look at BOURNS, which also makes superb quality potentiometers. All in all, it's always a trade off between precision, manufacturing quality and price. You will find that ALPHA pots are mostly present in Ibanez guitars as stock pots. A good benchmark, in my opinion, is to consider everything Ibanez uses stock (in hardware i.e. pickups, electronics, tuners) as complete crap. :lol:

    Hope this helps! :)
     
  15. GorillaSalsa

    GorillaSalsa SS.org Regular

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    Say I wanted to use no potentiometers with my guitar, how would this effect things? The OP says that more resistance = brighter tone, but I would think that zero resistance would mean a fuller tone, yes?

    EDIT: whoops, sorry about that! vvvvvvvv
     
  16. guitarneeraj

    guitarneeraj WindMarp Contributor

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    Please read all the replies in this thread, user Cannibalbritney describes and has implemented the kind of wiring you mention..
     
  17. Suitable

    Suitable SS.org Regular

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    ^ You noted 2 types of CTS pots, +/-30% and 10%. How do you work out which is which? Also for going 1 vol and 1 tone, 500k A pots would be best? And what brand/type caps are best? You said ceramic caps are shit, what are the other made from? Im about to change all the electronics in some of my guitars, so want to do it right the first time round.
     
  18. guitarneeraj

    guitarneeraj WindMarp Contributor

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    Well, you take a multimeter, measure the resistance and check which tolerance bracket it's in.. ;)

    Just checked the CTS website, they have a new series called 450G, the "Guitar Series".

    http://www.ctscorp.com/components/Datasheets/450g.pdf

    This datasheet clearly gives the part number you'd need to specify if ordering 10% or 20% whichever the case may be.

    For volume use an audio taper pot for sure. For Tone I would advise using linear taper, not many people like the feel of an audio taper pot for the Tone control.

    500k pots are not the "best", you can even use lower values like 250k or 100k(if you want lesser noise but can deal with a slightly darker tone). Depends what your goal is.

    There are many types of capacitors, depending on the material used for the dielectric. Polystyrene are the best for low values (upto 0.01MFD or so); beyond that they get bigger in size so then you use stacked metal film or metal film.
     
  19. Kingarchetheros

    Kingarchetheros SS.org Regular

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    does that mean that you can change the K value of a pot?
     
  20. conjurer_of_riffs

    conjurer_of_riffs SS.org Regular

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    Lets say that I have one volume and one tone. If I change from passive to active pickups or vice versa, will I have to change the volume and the tone pots or just the volume? Thanks in advance.
     

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