[music-dsp] digital equivalents of analogue filters

[Al Clark]

At 06:17 PM 8/13/01 +0800, Andrew Simper wrote:
>Does anyone know what digital filter types implement the following analogue
>ic's:
>
>CEM3320 (4 pole low, band and high)
>CEM3328 (4 pole low, perhaps just a hardwired CEM3320?)
>SSM2044 (4 pole low)
>
>Also does anyone know of any digital low pass filters that aren't one of:
>biquad (in all forms - direct form I/II etc etc)
>state variable
>4 onepoles with a feedback (moog)
>
>Thanks,
>
>andy
>--


You can implement digital filters many ways. The most direct conversion 
from an analog filter is probably bilinear transformation. This will 
generate an IIR filter. Another type of filter is the FIR filter. These 
filters can be (and often are) linear phase. They are also easier to design 
from a stability point of view.

No digital filter will be an exact replica of an analog filter even if you 
can discount aliasing.

You may want to read some DSP primers. A very good start would be Rick 
Lyons' book: Understanding Digital Signal Processing. I have seen this book 
at the local Borders and Barnes & Noble stores.

We manufacture a small DSP module and development kit that you can check 
out at our website:
www.danvillesignal.com. It features a Analog Devices ADSP-2186M, an AC-97 
audio codec and a flash based PIC loader.

Al Clark
Danville Signal Processing, Inc.
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