Thanks @Marin_Weigel for the info. It seems they’re using what is now a typical multi-bit delta-sigma architecture: preliminary oversampling up to 16x (depending on input rate) with a choice of filters, followed by a second 4x or 8x oversampling (to 64fs or 128fs), a 5-bit modulator and an equal-weighted (i.e. thermometer coded) output. Good to know.
I may be totally off base, but I would check how I set up your endpoint in the audio section of Roon. Is the ‘Max Sample Rate’ correct?
It appears that the N20 is syncing to an external clock at 176.6KHz which is why it’s upsampling, from the source which was 44.1Khz. I assume that the 176 is the clock from dCS because you are using an optical cable and 176 is the optimal rate. The ROON green light shows that there has been a change in the signal path and tells what has changed.
Hi Roony, @Marian and @Marin_Weigel are correct. The Vivaldi DAC always oversamples PCM input to either 705.6kS/s or 768kS/s (depending on whether the input sample rate is 44.1 or 48kS/s-based). It then, if you configure it to do so, optionally further upsamples to DSD64 or DSD128 before presenting to the ring for conversion.
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Well, it is 64fs or 128fs, but not DSD, since it’s a multi-bit modulator. Also, the second upsampling doesn’t seem optional.
We’re talking about different stages of the process. The oversampling to 705.6/768 is not optional, the subsequent upsampling to DSD/DSDx2 is.
The final modulation to a 5-bit signal, the purpose of which is to optimize noise shaping, is internal to the ring DAC and also not optional.
I would say there is no need to upsample within Roon if oversampling on the DAC is to such a higher level.
Sorry @Marian, I was thinking about a Rossini when I wrote my post above and mixed the two up in my mind. In the Vivaldi, where the upsampling is performed in a separate chassis, the Vivaldi Upsampler, the choice of oversampling to DXD, upsampling to DSD or DSDx2 or simply passing through the audio, is left to the user. The subsequent oversampling and modulation operations performed in the DAC are as you say not optional. My apologies!
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No worries. I figured you meant something like that.