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using a 250k and 500k pot in the same rig

Discussion in 'Pickups & Electronics [BG]' started by Jake555, Jun 18, 2016.


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  1. Jake555

    Jake555

    Nov 2, 2010
    Toronto
    err.. bass

    anyway, Can I do this? Or will the world implode?

    I have a humbucker bridge on order and it should have 500k, and the neck needs 250k.

    why is this a dilemma? Can I do this? What would happen?
     
  2. honeyiscool

    honeyiscool

    Jan 28, 2011
    San Diego, CA
    You could, but there's no such thing as one needs the other. I wire most single coils with 500k, too.

    The other thing is that on your average passive bass, all components are kind of interacting with each other all the time anyway and that all your best laid plans of isolating the different resistances per each pickup might be futile anyway.

    I'd just use 500k for everything, but that's just me.
     
    Jake555 likes this.
  3. Not only is it fine to do, but you might even find it desirable, in the pursuit of optimizing the taper of each pot to each pickup's impedance.

    Take note, however, that there is no such thing as 500k for the bridge pickup and 250k for the neck pickup. The pots combine to a total load that is neither value. For instance, at full volume, each pickup sees the reciprocal sum of both values, which is 166.67k Ohms. By contrast, two 500k pots yields 250k Ohms, while two 250k pots yields 125k Ohms.
     
    Jake555 and SteveCS like this.
  4. Jake555

    Jake555

    Nov 2, 2010
    Toronto
    Hm, well what I mean by 'needs' is that in the installation diagrams the manufacturer recommended 250k pots, so I feel inclined to do that. But now everyone says 500 all the way.

    Pertaining to 166.67ohms, what would happen if one were to go ahead and do it anyway? Would there be a grand fire? Would it be noisy? Would it simply not work?


    Anyway, questions aside, looks like I'm going 500k

    Thanks guys!
     
  5. 40Hz

    40Hz Supporting Member

    As @line6man suggested it may be worth your while to experiment a little before you button everything up. In addition to the interaction of components in a passive bass circuit, there's also variances in the components themselves. Most readily available pots have +/- 10% or 20% tolerances. So your average 250K pot can have a value as high as 275K or as low as 225K at a minimum on average.

    Same goes for your tone caps - which has led some people to believe the material the cap is made out of has a significant effect on the tone, when what they're most likely hearing is differences caused by the actual value of the cap, as opposed to the value that's marked on its casing.

    Suggestion: these components are fairly cheap if you buy them through electronic distributors rather than music supply sources. Get yourself a handful of capacitors of various types along with a pair each of 250K and 500K pots (try audio and linear taper while you're at it) and swap things around until you find the combination you like best. You'll learn a lot more doing that than poring over 20 how-to articles or Youtube videos and reading 200 forum posts about what's "best."

    I had a project bass awhile back where I did that. I experimented with strings and pups and components (while taking careful notes and doing focused listening tests) until I finally got almost the exact sound I was looking for. And I learned an awful lot about which pieces did what to the sound in the process.

    If I were to exactly duplicate each piece of that circuit on a new project it would probably sound different (possibly even better) because each of these components still have their individual variances. But at least now I know where I need to start to get in the general ballpark of this "ideal" bass sound I've got in my head. So next time out it'll be a lot easier (and cheaper) since I have a rough "map" to go by.

    So take some time and play around. It'll pay off in the long run.

    Luck! :thumbsup:
     
    Last edited: Jun 18, 2016
    rocknrollmouse, MovinTarget and pcake like this.
  6. 40Hz

    40Hz Supporting Member

    Either would work without anything bad happening. This is old fashioned micro-voltage Edison era analog electronics we're dealing with here. It's nothing like high-voltage analog (i.e. tube) or modern digital circuitry where a component choice outside the standard spec could result in fireworks or complete circuit failure.

    So play around. I'll usually at least start with the manufacturers' recommended circuit component values if it's something new to me like a brand of pup I never tried before. But that's me.

    If you go off the reservation, the worst that can happen is you don't like the way it sounds or how the controls behave. If that turns out to be the case you're only out some time and the cost of a few replacement parts.
     
    Last edited: Jun 18, 2016
    rocknrollmouse and petey293 like this.
  7. Don't overthink this. Practically speaking, the choices you make will have very little effect on anything. Mixing 250k and 500k is the equivalent of using two 330k pots. The difference between 250k and 500k is very subtle to begin with, and the difference between 250k and 330k, or 500k and 330k, is going to be even more subtle than that.
     
    JohnJenkins, MovinTarget and 40Hz like this.
  8. honeyiscool

    honeyiscool

    Jan 28, 2011
    San Diego, CA
    If you use a switch instead of the standard J bass wiring, then there actually is a point to using different values for different pickups, since a switch can fully remove a potentiometer from the signal path.

    But most basses don't use switches, so pots are always interacting with each other.
     
  9. Jake555

    Jake555

    Nov 2, 2010
    Toronto
    Ok wait, line6man - you were saying using a 500 as well as a 250 is going to work fine, and might even be desirable?

    And that it's the same as using two 330k pots. I'll definitely have to actually get my bass installed and start testing things. As many have said I suppose that's the only real way to achieve the frequencies from each that I want .. but.. is there a no compromise option? In theory at least? how come there isn't a way to wire the system so that they don't interact at all, they're totally ignorant of eachothers existence? The P Pup would get the tone knob and his volume, Bridge pup would just get its own volume. So therefore each pup can be happy in it's own zone.



    Well poopie, I've opened a can of worms. Kind of exciting though.
     
  10. Yes. The pots will work fine.

    There is no need for isolating the pickups. You don't need to have specific loads on them. They work just fine with a wide range of loads, and the difference between trying to do what you want, and accepting the reality of it is going to be so subtle that you would be wasting time to bother with it. If you want to use two different pot values, just go for it.
     
    MovinTarget, 40Hz and Jake555 like this.
  11. 39-Bassist

    39-Bassist

    Jul 7, 2010
    Florida
    Endorsing Artist for: Brace Audio; Duncan Pickups; Line6, Hipshot, GHS Strings, Somnium Guitars
    +2
    Don't over think it.
     
    MovinTarget likes this.
  12. Ric5

    Ric5 Supporting Member

    Jan 29, 2008
    Colorado
    I disclose nothing

    Rickenbacker used to put 250k ohm pots as volume pots and 500k ohm pots for tone pots in the 4001 basses ...

    This bass here has 250k ohm volume pots. The neck tone pot is 500k ohms and the bridge tone pot is 1000k ohms. Also the neck pickup has a toggle for single/series/parallel operation.

    oct%20054.jpg

    oct%20055.jpg

    oct%20056.jpg

    oct%20057.jpg
     
    Jake555 likes this.
  13. honeyiscool

    honeyiscool

    Jan 28, 2011
    San Diego, CA
    250 volume and 500 tone is often a great combo. I wired my PRS guitar that way to take off some of the ice pick while preserving brightness.
     
    Jake555 likes this.
  14. seanm

    seanm I'd kill for a Nobel Peace Prize! Supporting Member

    Feb 19, 2004
    Ottawa, Canada
    You can easily do this with a preamp, that is one of the advantages of an active bass.

    There are also mechanical ways: switches, two output jacks, a transformer. But generally they just aren't needed and add extra cost.

    I would just try the two pots first and see how it goes. You will most likely be perfectly happy with the results.
     
    petey293 likes this.
  15. honeyiscool

    honeyiscool

    Jan 28, 2011
    San Diego, CA
    Actually, I estimate that more than 90% of active preamps I've seen out there do not isolate the two pickups. They just combine the output from two volume knobs or a standard passive blend knob (which is essentially the same thing as two volume knobs) in parallel and then feed that to the input of a preamp, so volume pots are always interacting with each other. There are few systems that do featured buffered blend controls, like John East preamps or EMG BTS/BQS, but most systems do not even attempt to do this. Even many basses that have EMG active pickups do not bother with buffered blend controls and will combine the pickups by just combining the output of two 25k/50k volume knobs in parallel and then feeding that to the preamp, which does not isolate the pickups.

    If you have a buffered blend, then you get a fully usable blend of pickups at any volume. It's just something that very few stock basses even attempt to provide. It's one of the many reasons why I tend to prefer switches.

    The most clever preamp out there is surely on the John East preamp. Its blend knob is simply genius. It's a passive blend control when the preamp is set to bypass, but becomes a fully buffered blend control when the preamp is active.
     
    Last edited: Jun 19, 2016
    line6man likes this.
  16. Adding to this, when you have a buffered blend, or multiple buffered inputs, the pickups will not mix in quite the same fashion, as they will each see a constant resistive load from the buffer. The normal way of combining pickups with passive components lets the pickups load on each other, giving a somewhat different sound.
     
  17. Gideon352

    Gideon352

    Oct 17, 2003
    Gainesville, FL
    Definitely experiment! Pots are resistors. Think of them as resisting your high end. :thumbsup:
    The lower the pot value, the less high end you will have (more resistance). The higher the pot value,
    the more high end you will have (less resistance). :bassist:
     
    rocknrollmouse likes this.
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