Single-knob active EQ with a low-pass filter in place of a passive tone knob?

Discussion in 'Pickups & Electronics [BG]' started by EmaTheMirror, Jun 28, 2020.

  1. I mainly play passive basses, but that doesn't mean I'm against anything active as a concept, I even played only active ones up to say 13 years ago...

    ... anyway, yesterday I was playing around with a amp-sim plugin which has a full-parametric section inbuilt (it's the JTS Bassforge Rex Brown, by the way) and I saw how effective can be the use of the LPF (which has a fixed quite gentle slant, in that case) to control the high content of your tone and get finger definition/honky "a-la-Jaco" tone or find where you start to get too much fret noise, etc, as opposed to relying on the passive onboard tone knob and fixed cap. value. Yet, it still retains that sort of "organic" tone and immediate interaction you get with a passive tone control with more precision and without risking to get strange spikes/notches which can happen with traditional band EQs.

    I did a search here and I found this from a user, which is a rather close but more complex design:

    The Passinwind Open Source Preamp

    I was wondering: is there any commercially existing onboard tone option featuring a one-knob LPF as tone control? Would it be something very few people would take into account? Do you think that a passive multi-cap varitone would be a better option for this idea?
    Zooberwerx likes this.
  2. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    If it's too much work to DIY just the LPF section from my design I will be releasing a standalone design sometime this summer. I have PCB layouts ready to go, but the new standalone HPF board is first in the queue after I finish up the three fairly involved projects I'm currently in the middle of. The first version will be open source DIY (free, non-commercial), but I have received enough requests for commercial builds that I'm at least thinking about it. For myself I think the variable resonance is a key feature, but it would be no problem to omit it or just use a switch with a couple settings of your choice.

    Varitone cirsuits are cool but IME they provide a much different play feel than active solutions give. So as usual, "better" depends on what tradefoff set works better for your particular situation.;)
    Matt Liebenau likes this.

  3. I think that a one-knob LPF would unite the immediacy of a passive tone, but the ability to fine-tune the frequencies you want to roll-off, to a greater extent than varitones with fixed cap values, and that's without taking into account impedance and factors I'm not the most knowledgeable of. You want to just reduce some very high overtones? Roll off around 2,5/3 k - Less clank and a rounder sound on the top end retaining definition with no "blanket" effect? Say 1,5/1 k - "jaco-style" definition for fast finger playing without noise? Say 500 hz...

    ... I might be saying something not entirely accurate, correct me if I'm wrong. However, that's the kind of effect I got by keeping the tone wide open on the instrument and rolling of the LPF on the DAW at precise frequencies: every instrument and pickup has different resonant peaks and has such tonal proprieties set ad different frequencies, not even multiple caps can address that universally.

    P.S. In fact, I would always suggest to track a passive instrument with the tone full open and tame with your DAW or active hardware: your perceived round tone might sound dead in the mix and so on... that's why you want to shoot in RAW and not in JPEG... keep as much info as possible from the source when technology is involved.
    Torrente Cro and Passinwind like this.