[sdiy] What sort of filter is this?

[Nils Pipenbrinck]

Mike Beauchamp wrote:
> Excuse me if I get a few of the terms wrong here, but what sort of
> filter is neutral at it's middle position and then a high-pass and
> low-pass filter on either end?
>   
Just an idea:

You could use a high-shelf and a low-shelf filter and just connect the
outputs to a mixing pot. In the middle position you'll have just a bit
of gain, low-pass on the one and high-pass on the other side.

I threw together something like this and emulated it:

Schematic:

    http://torus.untergrund.net/misc/shelfmix1.png

Frequency response:

    http://torus.untergrund.net/misc/shelfmix2.png

The R7/R8 thing emulates a 1Meg linear pot btw..

Cheers,
    Nils