[sdiy] Digital Filter is GETTING closer

[Scott Gravenhorst]

Jim Patchell <patchell at cox.net> wrote:
>Major success tonight.  The four pole filter actually sounds like a four 
>pole filter.... (and I have 512 of them...to boot...).  This is more 
>filters than I have built in my entire life (well, analog ones that is). 
>  Resonance still doesn't work...(doesn't do anything....something isn't 
>connected correctly somewhere in the verilog code...).
>
>Putting the four pole filter in sure makes the oscillators sound a whole 
>lot better...it band limits them and takes the harshness (aliasing) and 
>sort of puts it in it's place...(it is still there, but nowhere near as 
>noticeable).
>
>On the XC3S1000 that I am using, I am up to 33% of the logic fabric, and 
>21 of the 24 block rams is being used.
>
>I looked at the output with a "logic analyzer" I did, and was very 
>impressed to see the waveforms turning gradually sinusoidal and the 
>cutoff frequency was lowered.
>

Jim, 

Very interesting.  Is there a chance we could see a block diagram of the filter?


-- ScottG
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-- Scott Gravenhorst
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