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Re: Filter poles...


>Date: Sat, 26 Apr 2003 18:24:33 -0600
>From: "Jesse Ray Lucas" <jlucas@neoprimitive.net>
>To: <Loopers-Delight@loopers-delight.com>
>Subject: Filter poles...
>
>Sorry to go OT here, but I have been looking around online and can't 
>figure
>out what the difference between a 4-pole filter and a 6-pole filter is.
>Does it have to do with the amount of gain that can be applied/cut by the
>filter?

It determines the steepness of the cutting curve, i.e. how fast the 
filtered signal falls off with frequency (filter rolloff, measured in 
dB/octave). In other words, the number of dB/oct is a measure of how much 
frequency will be attenuated for each octave beyond the cutoff frequency 
(each octave represents a doubling of the frequency : a 1,000 Hz sinewave 
is exactly one octave higher than a 500 Hz one for example).

The rolloff in dB is equal to 6*NP (NP being the number of poles).
Most filters used in synths etc. are either 2 poles (12dB/oct) or 4 poles 
(24dB/oct).

In effect, the most important thing is how the filter actually sounds ;)

</daviD>

"What sounds to you like a big load of trashy old noise
  is in fact the brilliant music of the genius, myself"
Iggy Pop