You can put a compressor/limiter or AGC circuit after the filter and it can boost or reduce the gain to compensate for the level loss the filter introduces.
-J

On Apr 22, 2010, at 1:24 AM, yahoo@... wrote:

>> Is it possible to make an analog filter where you can continuously
>> vary the cutoff slope I am imagining a bandpass effect where the
>> band gets continuously narrower and wider. Perhaps a voice is
>> filtered through, at first it sounds human but you continuously dampen
>> off all harmonics until it sounds like a sine wave.
>
> I do not remember a filter circuit with adjustable slope. The only solution
> I know is panning between several filter stages (e.g. the A-108 VCF with 4
> outputs followed by a VC mixer A-135 which is controlled by the A-144
> morphing controller). But that's not exactly the same as a control for the
> filter slope because one pans only between e.g. the 6dB, 12dB, 18dB and 24dB
> outputs of the filter.
>
> But you may get a similar result by increasing the resonance of a bandpass
> that has constant amplification at the filter frequency. Depending upon the
> filter design the level in the passband or at the filter point remains
> constant (or anything in between). In the first case the loudness increases
> while the resonance increases (because the power at the filter point is
> added to the passband power). In the second case the loudness decreases
> while the resonance increases (because the power in the passband decreases
> and the level at the filter point is constant). The two behaviours can be
> combined to obtain a subjective loudness that remains nearly unchanged while
> the resonance increases.
>
> Best wishes
> Dieter Doepfer
>
> P.S. We are working on a VCF with adjustable resonance behaviour
> (controllable between constant level in the passband or at the filter
> point). But it's not yet announced on our website as we have a lot of other
> products and modules in the holding pattern have to be released earlier.
>
>
>
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