[sdiy] FPGA Madness? (Was: NCO Jitter)

Mikko Helin maohelin at gmail.com
Sun Aug 5 07:56:16 CEST 2018


Single Xmos Xcore prosessor might be able to do the job.

--Mikko

la 4. elok. 2018 klo 19.34 Tim Ressel <timr at circuitabbey.com> kirjoitti:

> Okay, that was silly. I would need mondo processor power to do that. Looks
> like its FPGA time! Yay!  I like Xilinx so the questiob becomes how much
> FPGA do I need? Spartan-6?
>
> --timmers
>
> On 8/4/2018 9:14 AM, Tim Ressel wrote:
>
> Thanks everyone! It looks like the FPGA route is doable, although those
> CIC filters make me think I can do this on a processor after all. Maybe 2
> procs: one for handling MIDI and ADC tasks, and one as a oscillator core.
> Use SPI to write values to the osc core. NCOs are cheap so doing 9
> instances is no problemo. I need VCAs on each NCO but that is just a
> multiply. That might just work.
>
> --timbo
>
> On 8/4/2018 6:06 AM, Scott Gravenhorst wrote:
>
> Michael Zacherl <sdiy-mz01 at blauwurf.info> <sdiy-mz01 at blauwurf.info> wrote:
>
> On 4 Aug 2018, at 06:38, Scott Gravenhorst <music.maker at gte.net> <music.maker at gte.net> wrote:
>
> but I did it the "wrong" way by making an FIR filter with a
> huge kernel.  The filter did the job to remove most of the alias artifacts, but it
> did some weird frequency dependent amplitude things especially at the high end of the
> audio spectrum.  I later learned that it is better to use cascaded smaller kernel
> filters,
>
> Hi,
>
> “kernel† == order of the filter?
>
> m.
>
> Sorry, I neglected to state that the filter is a FIR type.
>
> FIR filters have a kernel of coefficients which define the impulse response.  The larger the
> kernel, the more definition one can have in the output spectral profile.  Larger kernels also take
> more time to compute which is a drawback of the FIR filter.  FIR filters can make good brick wall
> filters, that is, very flat response with steep roll off into the stop band.
>
> -- ScottG
> ________________________________________________________________________
> -- Scott Gravenhorst
> -- http://scott.joviansynth.com/
> -- When the going gets tough, the tough use the command line.
> -- Matt 21:22
>
>
>
>
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>
> --
> --Tim Ressel
> Circuit Abbeytimr at circuitabbey.com
>
>
>
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>
> --
> --Tim Ressel
> Circuit Abbeytimr at circuitabbey.com
>
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