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Re: Filter poles...
At 05:24 PM 4/26/2003, Jesse Ray Lucas wrote:
>Sorry to go OT here, but I have been looking around online and can't
>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
"pole" refers to an aspect of the mathematical description of a filter. I
guess the best way to understand it intuitively is to think of a frequency
response plot of a filter, which you have probably seen. They have
frequency along the x-axis and the gain on the y-axis. A pole will be an
inflection point along the frequency axis where the slope of the curve
changes negatively by 6dB/octave. For example a single pole at 5 kHz will
cause the gain to start sloping downwards, such that it will be 6dB lower
by 10 kHz. Several poles together means the slope changes that many times
more. So a 4-pole filter will have the gain slope change by 24dB/octave,
and a 6-pole filter will have the gain slope change by 36dB/octave. In
other words, the 6-pole filter is a more drastic gain cut than a 4-pole
The opposite of a pole is a zero, which is a point in frequency where the
slope changes more positive by 6dB/octave.
there's a lot more that goes into a filter design than that, but hopefully
this answers your question.
Kim Flint | Looper's Delight
email@example.com | http://www.loopers-delight.com