Using one of the StateVar Filter (Multi) can give us a very wide range of filtering options by mixing the outputs to combine their different characteristics in a number of ways.
Simple Low Pass filtering
Combining Low pass and Band Reject filtering.
Note how in this example we get both a notch and a strong resonant peak.
Combining High Pass and Band Reject filtering.
Note in the HP/BR example the peak has now moved higher than the notch frequency.
Combining Low, High and Band pass.
We now get a strong resonant peak giving a frequency boost, but not much in the way of any filtering out of frequencies.
A two mode alternative to the four mode filter.
This model uses the same filter, but we only use the Low and High pass outputs. The Low pass is fed directly to one input of the X-Mix module, whilst the High pass has the option of being fed through an inverter. The inverter affects the output frequency spectrum.
This is similar to those wonderful Oberheim Expander filters where you could cross mix the High and Low pass outputs. It won’t sound quite the same due to the chips that Oberheim filters used, but close to them.
High Pass in phase.
The frequency spectrum is fairly flat when HP and LP are in balance with no obvious resonant peak. Whereas below in the first example once the High Pass starts to predominate we get a notch with the resonant peak at a higher frequency.
And in this example where the Low Pass is starting to predominate we get a notch with the resonant peak at a lower frequency.
High pass out of phase.
By inverting the high pass output, we can create a strong resonant peak when both High and Low pass signals are in balance, whereas in the previous example where the High pass was not inverted the output is almost flat when the two signals are in balance.
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