I'm seeking to confirm whether it's possible to have granular control of when I engage the hi/low pass filters on the EHX mainframe "bit crusher" guitar pedal. I've digested about 5 youtube videos on the product but there are so many features/knobs/dials on this pedal that it's not practical to cover everything. None of them seem to touch on the exact use case I have in mind.

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It seems that the filter settings are controlled via switch, so that leads me to believe that expression pedal control of the hi/low filter isn't possible. Maybe I could try to use a volume pedal before the mainframe with my desired filter and bit depth dialed in, then maybe I'd have the granular control I'm after.


Can anyone with some hands-on experience with this product recommend or comment on a practical signal path / gear configuration if I want to have control over when I engage the hi/low filter?

If it helps, the items I have:

  • Boss volume pedal
  • 2 expression pedals
  • Can you add a link to the manufacturer's page or manual?
    – Theodore
    Commented Jul 21, 2022 at 14:01
  • What genre is this for? I think bit crusher is one of the most awful sounds. Commented Jul 21, 2022 at 18:35
  • 1
    @piiperiReinstateMonica I think it's actually a matter of taste and good usage of it...
    – Tom
    Commented Jul 21, 2022 at 21:28
  • @piiperiReinstateMonica currently trying some guitar dub-step sounds, but also wanted to try some futuristic sounding riffs. Not sure if you've ever played the 90s space fighter game descent 2, but that OST has some awesome riffs that have a tone thats part distortion part robot Commented Jul 22, 2022 at 0:42

1 Answer 1


Yes, this appears to be definitely possible. Not only does the product page advertize than any knob can be mapped from the expression pedal, the tips&tricks section also explicitly mentions this use case:

  • BPF – This is the previous two filters combined, providing some of the benefits of each. This can also be used for a wah-like sound when using an expression pedal, or a cocked-wah sound without an expression pedal.
  • The knobs can be mapped to an expression pedal, but the hi/low filter is just a flip switch (not a knob), which would be different, as I read it Commented Jul 22, 2022 at 0:40
  • No, the filter (-cutoff) is a potentiometer like everything else. Of course, there's a flip switch that selects what kind of filter this is. There's no such thing as continuously switching between different kinds of filter (other than mixing between them, which would cause phase problems). But tweaking the cutoff of a bandpass filter is essentially equivalent to morphing it between a lowpass- and highpass filter. Commented Jul 22, 2022 at 8:08

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