The Holters filter implementation seem to have a bit of a problem. Here are two similar filters, one is set to +5dB, the other to -5dB. You can see on the probed graph that they do not boost and cut in a symmetric way.
Where it gets very weird is when you actually notice that the dB boost/cut is spot on when you set the cursor to the max independently of what the max value is.
Here are some examples with the cursor set at max opposite.
Here's another example showing the difference when the cursor is not at the max.
Would be very nice to get this fixed or to have a workaround. Cheers.
edit: Changed the title to BUG REPORT
[edited by: CopperMaze at 11:56 AM (GMT -4) on 19 Sep 2020]