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What's the effect if i change potensio of IBZ EQB 3S preamp ?

Discussion in 'Pickups & Electronics [BG]' started by ferdianadek5, Dec 9, 2012.

  1. ferdianadek5


    Oct 17, 2012
    Hello everybody

    i wanna change value of my preamp's potensio, i have standar EQB 3S preamp, i wanna change value like bartolini MK1 or Bartolini NTMB

    this is the potensio value of EQB 3S
    Pots Balancer - POTENTIOMETER VOL/500K/SOLID
    Pots Middle - POTENTIOMETER 100K-B/SOLID
    Switch Tone selector - SWITCH 2-WAY TOGGLE BK

    i wanna decrease the value of :
    bass, treble, mid become 50K
    Volume still 25K
    Balancer become 250K

    this is the wiring of EBQ 3S, Bartolini MK1, Bartolini NTMB

    EQB 3S

    Bartolini MK1

    Bartolini NTMB

    the question is
    it's any effect when i change the value of my potensio ?
    i wanna change because the sound of my preamp, is domminant treble, the mid and low doesn't loud

    so i hope that you can answer my question

    Thank you :)

  2. The preamp will not function properly.
  3. ferdianadek5


    Oct 17, 2012
  4. Equalizers are usually built to function with components of specific values. If you change the value significantly, the behavior of the circuit also changes. This may be true of both the amplitude of the boost/cut, and the functional range of control throughout the rotation.

    In any case, changing the pots is not a desirable means of altering a preamp's voicing, and at best, you are looking at the tonality of adjusting the existing pots.
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  6. ferdianadek5


    Oct 17, 2012
  7. giacomini


    Dec 14, 2008
    Florianopolis - Brazil
    Endorsing: Copetti Guitars
    What else do you want to hear(read)?
  8. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    He wants to hear the answer he wants to hear!

    Changing the pot's value will not change the frequency of the control.

    That's not the answer he wants to hear. ;)
  9. Steve Dallman

    Steve Dallman Supporting Member

    The range of each control will not change. The actual control of the tone may be in a different part of the travel with the new pots, but you will not get more or less of the range of each control.

    I often use a Baxandall tone control preamp I have built since the mid 70's. I've built a lot of them. It is meant to have 250k audio taper pots. I've used smaller pots and pots as large as 1meg ohm. The preamp performs the same although with the 1meg pots, there is little control at the extremes of the pots.

    I've used a lot of Artec preamps that have 50k pots. When switching to stacked, concentric pots, I've subbed 100k pots. The controls work the same.

    To change what you want changed, would require component changes in the preamp itself, which wouldn't be possible.

    Since your pickups are passive, going to a 250k balance control would roll off high end slightly. THAT might get you closer to what you are looking for. You could add an internal tone trimpot, wiring a standard passive tone control to the circuit on the output of the blend/balancer control (yellow wire.) Perhaps a 500k trimpot in series with a .01uF cap, wired from yellow to ground. Roll off the treble you want, and close up the cavity.
  10. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    I've done the same thing with the same results.
  11. Tonibassist


    Apr 4, 2015
    I use EQB III SC, and i change pot value:
    Vol: Pushpull Noble 25K
    Blend: Noble 50K
    Mid: Pushpull freq Noble 50K
    Bass & Treble: Stacked 50K
    Ground cable: AWG Vintage Cloth
    Pickups Bartolini M34CX Usa
    Sound is really nice, more detail & clarity
    Before use EQB i use OBP3, My opinion I more like to EQB.. more detail for EQ.
  12. Tonibassist


    Apr 4, 2015
    Sorry my blend use 250K

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