[sdiy] Electrosmith Eurorack DSP platform

Mike Bryant mbryant at futurehorizons.com
Fri Jan 28 12:40:59 CET 2022


That would be a magic goal.  And probably transgressing every law of physics :-)

What we did in a class D amp we designed as a demonstrator is first measure the elements causing distortion in the output signal and then dynamically calculate and add a compensation signal to it.  A bit like feed-forward does in an analogue amp.  A lot of DSP required though.  And you never get to perfect.



-----Original Message-----
From: cheater cheater [mailto:cheater00social at gmail.com] 
Sent: 28 January 2022 11:34
To: Mike Bryant
Cc: Eric Brombaugh; synth-diy at synth-diy.org
Subject: Re: [sdiy] Electrosmith Eurorack DSP platform

Can you create two signals so that the distortion harmonics are flipped, and thus cancel out completely?

On Fri, Jan 28, 2022 at 11:44 AM Mike Bryant <mbryant at futurehorizons.com> wrote:
>
> His THD isn't due to aliases, it's due to switching errors.   If you put two outputs in timesync with each other then you'd reduce noise by 3dB but the harmonic distortion would remain the same.  Offsetting one in time from the other means you have two smaller harmonic causing spikes of half the amplitude, which reduces the actual power in the harmonics ....  maybe :-)
>
> -----Original Message-----
> From: cheater cheater [mailto:cheater00social at gmail.com]
> Sent: 28 January 2022 10:38
> To: Mike Bryant
> Cc: Eric Brombaugh; synth-diy at synth-diy.org
> Subject: Re: [sdiy] Electrosmith Eurorack DSP platform
>
> The aliases would still be reflecting off the same sampling frequency
> - how would that have the effect of a higher sampling rate? Am I 
> missing something? Thanks
>
> On Fri, Jan 28, 2022 at 10:45 AM Mike Bryant <mbryant at futurehorizons.com> wrote:
> >
> >
> > On Thu, Jan 27, 2022 at 11:00 PM Eric Brombaugh via Synth-diy <synth-diy at synth-diy.org> wrote:
> > >
> > > I was seeing harmonics down slightly better than 80dB with all the 
> > > mitigation measures active. Without it was more like 60-65dB. Not 
> > > quite as good as even an inexpensive sigma-delta I2S audio DAC, 
> > > but a few SMT passive parts beat that for cost & simplicity and 
> > > I2S DACs don't support 12MHz sample rates.
> > >
> > > Eric
> >
> > Did you try running two systems in parallel with the second running half a sample behind and summing the pair ?   Might give a little bit performance as it would have the effect of an even higher sampling rate.
>





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