[sdiy] FPGA synth I have been toying with for a while

[Scott Gravenhorst]

Jim Patchell <patchell at cox.net> wrote:
>Nope...exactly the same problem.  :-(....although, at 192KHz sample 
>rate, the max cuttoff would be ~32KHz...and around 8KHz is really all 
>you need...

For what it's worth, I did some informal experiments with a digital SVF (which is
different than your approach, so this may be totally nonsequitur) at sample rates of
1MHz, 500Kz, 250KHz and 125KHz.  I'd bet you already know this, what I found was that
using waveforms with fast transients, the higher the sample rate, the more "freq" and Q
range it had before going bonkers.  I did not band limit my waveforms.  At 125KHz, I
was disappointed in the ranges of both Q and freq.  The filter was usable, but the
range was too truncated for my liking.  Now I wish I had kept the numbers...

I am very interested in how this goes...

>Scott Gravenhorst wrote:
>> Jim Patchell <patchell at cox.net> wrote:
>>> Well...sort of...I guess... :-)
>>>
>>> It is going to be a model of a standard 4 pole low pass fileter...with 
>>> resonance.  I was just going to do a state variable filter...but, 
>>> thought I would try the four pole instead.
>>>
>>> in ->DIFF-----MULT---->SUM----->Z-1------ out
>>>       ^        ^       ^              |
>>>       |        |       |              |
>>>       |      freq      |              |
>>>       |                |              |
>>>       +----------------+--------------+
>>>
>>> 	That is a rough idea of each pole section...four of those 
>>> cascaded...with feedback around the whole mess.
>> 
>> Will this method avoid the dreaded 1/6 sample rate restriction 
>from which the SVF suffers? > > >> -Jim >> >> Scott Gravenhorst 
>wrote: >>> Jim Patchell <patchell at cox.net> wrote: >>>> Hopefully, 
>I can keep the momentum up on this project. My hope...to >>>> 
>show it off at the last PNW Synth DIY meet in October. >>>> >>>> 
>http://www.noniandjim.com/Jim/dsm1/DigitalSynthesizerModule.html 
>>>> Hey Jim, >>> >>> Looks very interesting, have you decided on 
>a specific filter topology yet? >>> >>> -- ScottG >>> >>> 
>----------------------------------------------------------------- 
>>>> >>> -- Scott Gravenhorst >>> -- GateManPoly - FPGA Based 
>Polyphonic MIDI LA/FM Synthesizer >>> -- GateMan-III - FPGA Based 
>Monophonic MIDI LA/FM Synthesizer >>> -- PolyDaWG/8 - FPGA Based 
>8 Voice Polyphonic MIDI Synthesizer >>> -- FatMan: 
>home1.gte.net/res0658s/fatman/ >>> -- NonFatMan: 
>home1.gte.net/res0658s/electronics/ >>> -- When the going gets 
>tough, the tough use the command line. >>> >>> 
>_______________________________________________ >>> Synth-diy 
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>http://dropmix.xs4all.nl/mailman/listinfo/synth-diy >>> >>> >> -- 
>>> ---------------------------------------------- >> Visit 
>http://www.noniandjim.com >> SDIY: 
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>---------------------------------------------- >> > > -- ScottG > 
>> 
>----------------------------------------------------------------- 
>> > -- Scott Gravenhorst > -- GateManPoly - FPGA Based Polyphonic 
>MIDI LA/FM Synthesizer > -- GateMan-III - FPGA Based Monophonic 
>MIDI LA/FM Synthesizer > -- PolyDaWG/8 - FPGA Based 8 Voice 
>Polyphonic MIDI Synthesizer > -- FatMan: 
>home1.gte.net/res0658s/fatman/ > -- NonFatMan: 
>home1.gte.net/res0658s/electronics/ > -- When the going gets 
>tough, the tough use the command line. > > 
>_______________________________________________ > Synth-diy 
>mailing list > Synth-diy at dropmix.xs4all.nl > 
>http://dropmix.xs4all.nl/mailman/listinfo/synth-diy > > 
>
>-- 
>----------------------------------------------
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>----------------------------------------------
>

-- ScottG

-----------------------------------------------------------------

-- Scott Gravenhorst
-- GateManPoly - FPGA Based Polyphonic MIDI LA/FM Synthesizer
-- GateMan-III - FPGA Based Monophonic MIDI LA/FM Synthesizer
-- PolyDaWG/8 - FPGA Based 8 Voice Polyphonic MIDI Synthesizer
-- FatMan: home1.gte.net/res0658s/fatman/
-- NonFatMan: home1.gte.net/res0658s/electronics/
-- When the going gets tough, the tough use the command line.