Adding passive circuit to an Aguilar OBP-3, How to??

Discussion in 'Pickups & Electronics [BG]' started by Skywalker83, Jul 23, 2009.

  1. Is it possible to add a passive tone circuit into an Aggy OBP-3 circuit, the active OPB set up i will have is

    stacked Treb/Bass, Mid, Mid freq select switch, Blend, Vol.

    Is it possible to add a passive tone and volume circuit into the Aggy setup?

    If so , how?
  2. Yes, it's possible.

    Take the output from the volume pots and run it to the third terminal of the tone pot, then run that to the input of the preamp.
    Place your capacitor from the second terminal of the tone pot to ground.

    I'll do a diagram if necessary...
  3. Thanks, any chance you can do a diagram? using that Page 2 diagram in photoshop or something and adding the tone pot?

    Also, would i need 2 vol controls, one for the active and one for the passive? or would the single vol control do both circuits?
  4. I'll do a quick edit to that diagram so you can see where the tone goes.

    These are 250K/500K volumes, before the preamp, so they will function in passive mode.
  5. Zombbg4


    Jul 15, 2008
    Oh're the greatest. You will have some PM's soon when I get going on my project.
  6. :D Cool. Thanks.
  7. Great, thankyou !

    I have no idea what value if vol pot is coming with the Aguilar preamp (which i ordered from best bass gear), should the tone pot be of same value as the Vol pot?
  8. If you don't already have a preference for tone pot values, i would suggest 500K.

    When a tone is all the way up, some signal is still being cut, so the higher you make the value, the brighter the tone will stay with the tone on full.

    If you're willing to do a push/pull switch, you can bypass the tone control when you're not using it:

    As far as capacitor values, if you don't already have a preference, i would stick with a 0.047uF.
  9. Cool, so the push/pull means that in passive, you can have either vol, tone and blend, or just volume and blend?
  10. The volume and tone controls as well as the tone bypass switch will work in both active and passive mode.

    The tone bypass switch removes the tone control to maintain the regular tone without the extra capacitor in the circuit.
  11. so, its like 2 tone controls in one pot? One with a capacitor and one without??? Or does the push pull, actually switch the the tone pot "on and off"?

    ALSO, one more request for you Line6man...... how would i add an L.E.D onto the DPDT active/passive mini switch so that the L.E.D was on in active mode and off in passive mode?
  12. No, the push/pull turns the tone control off. When it's bypassed, the pot will not have any function.

    As far as an LED, I'm currently working on a project with an OBP-1, and i was originally going to do almost the same thing that you want to do, but i was going to do a bi-color LED for active and passive.

    According to the Aguilar diagram, the input of the preamp should be shorted out in passive mode. I'm not sure how it matters because the output is removed from the circuit, but i would rather not mess with it, so i am going to just do a power LED rather than active/passive LED's.
    I'm doing a push/pull switch, but if you want to use a 3PDT toggle switch and use the third pole for the LED, that is definitely do-able.

    Here was my original schematic for the LED, if you want to mess with it:
  13. The L.E.D might be something i look at in the future, i was more keen to add a passive tone circuit into the preamp.

    I've got a few 1M 1W metal film resistors kicking around somewhere, do you reckon those would be fine for the Mid switch?
  14. stflbn


    May 10, 2007
    I've got a complicatedly wired Schecter that has custom Kent Armstrong dual coil humbuckers in it and OBP-3. It's wired V/V/B/M/T with each Vol being a Series/Parallel Push/Pull Pot, then and Active/Passive mini-switch, but no passive tone control. It was all wired up by Brian at Low End, but the wiring is so voodoo to me that I've as of yet been hesitant to try adding a passive Tone control to it as I don't really want to add yet another Hole/Pot to the bass.
  15. Does there need to be a ground wire from the bridge added into the OBP-3 preamp (with the tone mod) set up?
  16. Your bridge should always be grounded.
    Ground the bridge to the nearest ground point.
  17. So , back of the added tone pot where the other cap leg goes would do?