Big Muff Pi style tone controls

Discussion in 'Pickups & Electronics [BG]' started by Xapt, Sep 20, 2018.

  1. Xapt


    Sep 19, 2018
    I wasn’t satisfied with the preamp on my Cort GB75. While the slap switch feature was my favourite, the treble and bass boost/cut just not enough to my taste. I was thinking of going in passive mode only but a standard tone pot simply didn’t do any mid-scoop. I read someone used an inductor but it was expensive and hard to find in local store.

    So I drew a schematic based on Big Muff Pi tone control which some hated because of its mid-scoop effect. I tried a few cap values for treble (bass cut) to fit with my desirable, but then hard to decide the value for bass (treble cut). A common 0.047uF is acceptable, but sometimes I need more than that.

    The solution is to have a switch for a combination of 0.047uF/0.01uF for medium bass/treble/mid-cut and 0.1uF/0.001uF for deeper bass/treble/mid-cut. The downside of using 0.1uF is the slightly reduced volume.

    With this schematic, wherever both bass and treble are set in any same position it will produce the same tone (and get the lowest mid). Start all from 0 position, moving bass to higher position will have the standard tone effect, but if moving treble you will start losing the low frequency and thinking you are playing low notes on a guitar. This is by design I do prefer. The mid control is just to neutralize the mid-scoop effect but I haven’t tried it on my Cort as there’s no more space.

    I use a dual stack 100K/100K pot for bass/treble, and the original 25K push/pull volume pot (because it supposed to be using preamp?) and it seems to work fine. Should I change it to 250K?

    Additionally, I put a serial/parallel switch for my dual J pickups. The balance pot will have the work on parallel mode only, and is bypassed when in serial mode.

    So far I’m satisfied with the configuration. The tone colour option are so wide that I always keep tone controls in the amp flat. Well no, actually I still need to have the low frequency a boost.

    Did I still miss out something here?

    Last edited: Sep 20, 2018
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