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Adding the passive tone pot to active preamp?

Discussion in 'Pickups & Electronics [BG]' started by nemo, May 5, 2008.


  1. nemo

    nemo

    Joined:
    Mar 19, 2004
    Location:
    Czech
    I use Aguilar OBP-3 preamp. Its treble frequency is at 6,5 kHz.
    What I don't like is that cutting the active tone knob does not tame the highs as I would like to.
    Do you think it would be possible to add the passive tone knob with capacitor to the end pair of wires after the active circuit, the same way as you would do with output wires after volume pot in passive bass?
    I am not any electronic expert, it is just a thought. Would that work or are there any catches?
     
  2. mjolnir

    mjolnir Thor's Hammer 2.1.3beta

    Joined:
    Jun 15, 2006
    Location:
    South Houston, TX
    Technically it would. I have my Marcus Miller wired so the tone control affects both active and passive mode and I've never had any problems with it.
     
  3. McSpunckle

    McSpunckle

    Joined:
    Feb 15, 2008
    It's very possible.

    A lot of active systems come with them. Just wire it like normal... before or after the EQ.



    The only issue is that tone knobs do, in fact, effect your overall tone. They always roll off a little bit of treble. Fender sells no-load pots that fix this... or a 500K pot isn't that bad.
     
  4. nemo

    nemo

    Joined:
    Mar 19, 2004
    Location:
    Czech
    Thanks for the replies.

    So that's cool, it looks like much cheaper and easier solution than getting some another active electronics with different treble frequency point.

    I had another idea - to avoid drilling another hole, I can just take out the active treble pot from its hole, put it into the cavity (isolated so that it doesn't short-circuit anything) and put on its place the passive tone pot.
    This way I can use the passive tone pot on the front of the bass for taming the highs as necessary, and still have the active treble pot available in the cavity in case I would need to increase the overall treble level.

    I usually don't add highs anyways, so for me it would be ok to have cut only passive treble pot on the front that when fully opened will have treble level as set by the active tone pot inside (I suppose it'll be flat or slightly increased).

    Isn't it ingenious or what? :D
     
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  6. basadam

    basadam

    Joined:
    Nov 29, 2005
    Check the Aguilar site for OBP-3 wiring. You'll see that passive signal gets blended before going into circuit. This is the best place to add a passive tone control (Sadowsky does it like that). Check OBP-1 wiring for how to add a passive tone control.

    As per "not drilling a new hole" issue; what you think will surely work, but a better idea would be to get a 50K stacked pot - that's two pots in a single hole. That way you won't lose the treble pot, you'll never know when it'll come handy. I believe bestbassgear.com should be able supply the pots and knobs you need.
     
  7. nemo

    nemo

    Joined:
    Mar 19, 2004
    Location:
    Czech
    Yes, I thought about the stacked 50k pot, but guessed a separate 500k pot would be better.. or doesn't it matter?
     
  8. McSpunckle

    McSpunckle

    Joined:
    Feb 15, 2008
    You'd want a 500K or 250K for tone, but you could stack the active controls together to free up a hole.

    A 50K tone pot would be the same as having a tone knob rolled down almost all the way... constantly.
     
  9. basadam

    basadam

    Joined:
    Nov 29, 2005
    You got it confused. A stacked 50K pot is needed to free up a hole for the passive ton pot. Passive ton pot needs to be 250K or 500K or even 1M.
     
  10. nemo

    nemo

    Joined:
    Mar 19, 2004
    Location:
    Czech
    Excellent, now all is clear! Thanks!
     
  11. MarkA

    MarkA Registered Schmoozer. Supporting Member

    Joined:
    Sep 26, 2008
    Sorry to revive an old thread, but, hey, at least I'm using the search function!

    I'm looking at a bass with a single, Nordstrand Music Man style humbucker and the accompanying Nordie, Stingray-style two band EQ (Bass and treble). I'd like to add a passive tone control to this setup, but have been told that it can't be done with this preamp. Any special reason that this should be the case? I usually find a passive tone more useful than most active preamps, so it's a feature I'd like to have! (I have basses with one or the other, but not both.)

    Would the fact that the signal from an active pre is likely hotter (in terms of volts? amps? both?) than a passive setup affect the do-ability of this? Would it affect which pots I can/should use?

    Finally, some people have recommended a no-load pot to me, while others have said that it "just accentuates the resonance frequency." Any thoughts on this? Seems to me that a no-load pot, in the last, "unloaded" part of its travel, should be just like wiring the pickup straight to the jack. (This is for my passive P-bass, but could apply as well to the active preamp + tone pot scenario.)

    Thanks in advance for any help.
     
  12. goran

    goran

    Joined:
    Dec 17, 2002
    Location:
    Croatia
    I want to know the same...

    ...and add my question:
    So I have a jazz bass with passive pickups and Aguilar OBP-3. If I understood correctly, the passive tone should be added between pickups and electronics?
     
  13. khutch

    khutch Praise Harp Supporting Member

    Joined:
    Aug 20, 2011
    Location:
    suburban Chicago
    If you want it to behave more or less like the tone control in a passive bass then, yes, you should put it before the preamp. If you put it after the preamp it will have some effect but not the same as on a passive bass. No load pots are fine, if you don't like the full bright setting you just turn it down slightly just as you would on a normal tone pot.

    I am not familiar with Nordstrand pickups or preamps at all. If the pickup is active as well as the preamp then putting a tone control anywhere probably will not be satisfactory. If the pickup is passive then I don't know why you could not put a passive tone control between the pickup and the preamp.

    Ken
     
  14. goran

    goran

    Joined:
    Dec 17, 2002
    Location:
    Croatia
    Yes, that is the plan - to have fully functional passive bass (Nordstrand NJ4s are passive) with the option to go active when needed, and still be able to use the tone pot in both active and passive mode. Thank you!
     
  15. goran

    goran

    Joined:
    Dec 17, 2002
    Location:
    Croatia
    I've found something that may work: Delano Control Pot 50K+250K. If I understand it correctly, two pots share the same shaft so the 250K is used passive mode, while 50k is used in active mode.

    This is a diagram for Delano Sonar preamp.

    Can it be used with any other preamp?
     
  16. line6man

    line6man

    Joined:
    Jun 20, 2008
    Location:
    Close to Los Angeles, CA
    Don't put the tone control after the preamp. It should go before the pickup, where it can interact with the impedance of the pickups.
     
  17. goran

    goran

    Joined:
    Dec 17, 2002
    Location:
    Croatia
    I understand that, but if I'm reading the diagram correctly, depending on the position of active/passive switch, the pot is placed before electronics(P) or "in" (A).
     
  18. line6man

    line6man

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    Jun 20, 2008
    Location:
    Close to Los Angeles, CA
    Nope, it is two different pots sharing one shaft. One pot is a passive tone, and the other is for the preamp's treble control.
     
  19. goran

    goran

    Joined:
    Dec 17, 2002
    Location:
    Croatia
    Are you saying it doesn't matter that each pot has separate terminals? -Meaning that in passive mode only the 250k works (preamp and 50k pot bypassed); while the 50k pot works only in active mode (250k pot is bypassed in this case). Not trying to be rude, just telling how I read the diagram because I don't think we're on the same page.
     
  20. line6man

    line6man

    Joined:
    Jun 20, 2008
    Location:
    Close to Los Angeles, CA
    If this is like the pot used in the Dingwal basses with OBP-3s, the pots don't really work at the same time. Turn it one way, and you have a passive tone control, turn it the other way and you have an active boost. If the preamp is bypassed, then the pot doesn't do anything when you boost.
     

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