Stereophile's measurements of dCS Vivaldi DAC
Posted 9th January 2014 at 03:59 PM by abraxalito
John Atkinson's 'WOW!' (more than once) to his measurement results from the Vivaldi DAC prompted me to have a closer look at how it does for noise modulation.
The AP's FFTs shown don't come with details about the number of points in the FFTs, so noise estimates are a tiny bit tricky. However there is enough detail to make some reasonable estimates.
I've attached the plot from which I'm making my estimates - if anyone notices I've made a slip-up, please do comment and correct me.
The red line shows white noise at peak level of -4dBfs. I generated white noise in Audacity at this level to compare - with the maximum 16k point FFT and BH windowing, I got the same level of noise as on this plot - -42dBfs in 22kHz bandwidth. That suggests to me that the FFT shown has 64k points.
Another way to estimate the noise is by looking at the difference between the blue plot (19.1kHz, 0dBfs) grass and the red. To my eye, the difference in level is 76dBr (-42 to -118dBfs). Given the red plot peaks at -4dBfs, this means the noise when playing out the tone peaks at -80dBfs. Thus there's about 13.5bits of dynamic range. I shall have to see what my Ozone gives with a similar test but at first blush this doesn't look too impressive for such an expensive bit of kit.
Have I made an error somewhere? Check for yourselves here : https://www.stereophile.com/content/d...m-measurements
The AP's FFTs shown don't come with details about the number of points in the FFTs, so noise estimates are a tiny bit tricky. However there is enough detail to make some reasonable estimates.
I've attached the plot from which I'm making my estimates - if anyone notices I've made a slip-up, please do comment and correct me.
The red line shows white noise at peak level of -4dBfs. I generated white noise in Audacity at this level to compare - with the maximum 16k point FFT and BH windowing, I got the same level of noise as on this plot - -42dBfs in 22kHz bandwidth. That suggests to me that the FFT shown has 64k points.
Another way to estimate the noise is by looking at the difference between the blue plot (19.1kHz, 0dBfs) grass and the red. To my eye, the difference in level is 76dBr (-42 to -118dBfs). Given the red plot peaks at -4dBfs, this means the noise when playing out the tone peaks at -80dBfs. Thus there's about 13.5bits of dynamic range. I shall have to see what my Ozone gives with a similar test but at first blush this doesn't look too impressive for such an expensive bit of kit.
Have I made an error somewhere? Check for yourselves here : https://www.stereophile.com/content/d...m-measurements
Total Comments 1
Comments
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Thanks for pointing out the review - I won't comment on the noise modulation aspects for now, but was pleased to see Fremer's take on the sound. As a very staunch advocate of analogue, vinyl "sound" his realisation that digital playback done right 'works', is yet another small step forward in getting the message out there.
Of course it's ridiculous that such an expensive setup was required, but it seems that this is what it takes at the moment for manufacturers to be able to get solid results in customers' unknown enviroments.
Hopefully other makers will get the message, and pull their collective fingers out ... :)
FrankPosted 10th January 2014 at 12:10 AM by fas42
