[sdiy] Electrosmith Eurorack DSP platform

Tom Wiltshire tom at electricdruid.net
Fri Jan 28 14:25:53 CET 2022


That's kind-of the idea of the "linearisation" diodes on the 13700 OTA. They essentially provide an "anti-distortion" which cancels (some of) the later tanh distortion of the input stage. But it's two stages one after the other that cancel, rather than two signals that are added together that cancel like your example.

Tom


> On 28 Jan 2022, at 11:34, cheater cheater via Synth-diy <synth-diy at synth-diy.org> wrote:
> 
> 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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