Swapping the filter-based preamp in a Fernandes FAB180 with the ACG01

Discussion in 'Pickups & Electronics [BG]' started by Ferniff, Apr 30, 2019.

  1. I have the poor man's Alembic. It's a great bass, great sounds and variety but it just doesn't get enough low end for me. The resonant low pass is cool but that only gives me more treble. I never found a need for the sweepable mid-boost. The ACG 01 seems like it can filter way lower than what I currently can and being able to adjust the gain at the cutoff is a plus. Thoughts? I still need to open up the bass to see how exactly it's wired and then find myself a ACG preamp.
  2. sikamikanico


    Mar 17, 2004
    That doesn’t sound right, are you using it correctly? A low pass filter cuts (well, filters) the highs, not sure how you’re getting more treble?

    Also, technically you won’t get more low end with filter electronics, you’ll just filter out more of the rest. Do you want to filter down to a lower frequency?
  3. Passinwind

    Passinwind I know nothing.

    A resonant LPF does in fact boost highs (or whatever frequency the frequency control is centered at) when resonance is set high.

    There's some explanation and a few links to other resonant LPF threads here: The Passinwind Open Source Preamp
    sikamikanico and ctmullins like this.
  4. sikamikanico


    Mar 17, 2004
    Right, but once you sweep pass the treble/high frequencies, they’re practically out of the equation, no? Unless, I suppose, you’re filtering just one of two pickups...
  5. Passinwind

    Passinwind I know nothing.

    If you sweep lower in frequency it'll boost lower. Alembic is the poster child for that mode, and in that case, separate filters per pickup is typically part of the method. I have zero experience with the ACG/East preamps though.

    My OS design that I linked to is a whole different thing, I really didn't want to do a knockoff of any of the existing commercial builds. If you want more bass you just turn up the bass control...what a concept! [​IMG]
    sikamikanico likes this.
  6. I also use synths so I'm familiar with resonant filters. The bass just naturally leans more on the treble/bright side. It's loud and also the cleanest sound I ever had in a bass, but I also have to boost the bass on my EQs first. The documentation for the ACG preamp states the filter goes as low as 70hz. With a resonant boost at that cutoff or near it, it will indeed be very bassy. The current stock preamp does not seem to go that low nor do I have control over the gain at the cutoff point. It's very versatile as is, except for in that regard