Adding more treble cut to Aguilar OBP-3

Discussion in 'Pickups & Electronics [BG]' started by Aloe, Apr 30, 2017.

  1. Aloe


    Apr 10, 2016

    I've swapped the preamp in my bass with OBP-3 and am really surprised how bright this preamp is (compared to the previous one). That is: I cut all the treble on the preamp and still have to notably cut it at the amp to get a tone I like. Is there a way I can make it sound darker?

    I understand that one possibility is to add a passive treble control in addition to the preamp's one. But that would need another hole in my guitar, so trying to avoid this solution.

    The guitar is Yamaha TRBX-505. Preamp is OBP-3. Wiring is 500k vol, 220k balance, stock 50k pots for the preamp. Swapping the volume for 250k would withdraw some treble, but I think I will need it darker.

    Would adding a capacitor to the treble pot help? Or something like this?
  2. ddnidd1

    ddnidd1 Supporting Member

    You can't just add a capacitor to the treble pot. The active circuitry is entirely different from passive circuitry.

    You could add passive treble rolloff circuit using a trimpot (and capacitor) inside the control cavity if you always like the high end rolled off.
    Last edited: Apr 30, 2017
    Aloe likes this.
  3. The trick is to add a capacitor and maybe a resistor to the volume pot. IOW, a tone pot. This can be soldered directly to the volume pot. Personally, I'd just clip in a test jig with a pot and try a few caps, then use the nearest resistor to the pot's final setting.

    As ddnidd1 said, you could also use a trimpot.

    Perhaps you can use a stacked control? Either stack your treble and bass together to leave a hole for a passive tone pot. Or perhaps switch your volume pot for a stacked concentric pot so you get the passive tone pot underneath the volume.
    Last edited: Apr 30, 2017
    Aloe likes this.
  4. wcriley


    Apr 5, 2010
    Western PA
    If you can get a sound you like by cutting at the bass and at the amp, I don't see the problem.
    Aloe likes this.
  5. Aloe


    Apr 10, 2016
    The more time passes the more I like the resulting sound. After tweaking the EQ on other bands it does not sound as trebly. Thanks everyone for the suggestions.
  6. Change the volumes to 250K. This will make a bigger difference than you think. I think if you added the passive tone, too, all of your problems would be solved. You could potentially change the 50K pot to a 25K and get more boost or cut, but it will also change your freq center/s, so that might not be a good option.
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