filter waveform question

[Toni Jovanovski]

At 11:02 18-08-98 +0200,  Ingo Debus wrote:

>> Filter design.There is a lot of analogue filters , like Butterworth ,
>> Chebyshev I & II ... But in a synth design with simple waveforms ( saw ,
>> pulse , triangle ) it's a question of luxury.
>
>On a second-order filter (12dB/oct) it is the Q parameter that
>determines whether the filter is a Butterworth or Chebysheff or
>whatever.

Well,I'm not so sure.I'm must check this ( I hate this complex math
).Butterworth and Chebysheff filter is a IIR ( infinite impulse response )
filter.There is a another class of filters FIR  ( finite impulse response
)filters.I say this because I wanna show how complex is Filter design.It's
not just electronics...


>> I think , in synth-design , that fourth-order VCF ( four poles in same
>> place ) is fairly enough.
>
>But the poles move when Q is changed, don't they?
>

Yes , of course!!!I forgot to mentiot it.When there isn't resonance ( Q )
the poles are simple ( real numbers ) and when you put resonance , poles
become complex-conjugate numbers.Changing the Q factor poles are moving in
complex-plane!The pole moving is in a circle line ( about this I'm not so
sure ).Thank you for the remark.

Toni Jovanoski