Hi I know a lot DAC’s perform internal upsampling of the incoming signal as part of the processing to analogue. Do the Naim DAC chips do this at all, looking at the one in my Atom as an example and if so to what do the resample to, max supported pcm?
Hi, the ND555 DAC implementation is described in the following white paper, There are white papers on the Naim site for other devices as well.
Doesnt seem to be one for my Atom. I see that the ND555 does oversample incoming signals though. So it may or may not do the same for the Atom. Any ideas what dac chip they are using in the Atom
Info from Naim:
272 - 21489 dsp
ndx, nds, nd5xs, superuniti - 21369
nDac - 21369. This was the original product that introduced the dsp tech.
dacV1 - 21489
Atom, Star, Nova, ND555, NDX2, ND5XS2 - 21489 with new programmable clocking system.
Isnt that the SHARC processor not the DAC chip?
Hi… it does vary on product, but most Naim DACs disable the internal converter filter and oversampler and off load to a seperate processor. The streamers for example use an Analog Devices SHARC processor which is optimised for DSP operations. That processor oversamples and performs the sinc low pass filter function prior to sending the processed data stream to the converter(s).
With devices like the PCM1704K as used in the ND555, this allows Naim (and other manufacturers) to run the converter at a higher sample rate such as 768kHz as opposed to its native 98kHz if it used its internal inbuilt oversampler and digital filter. These higher sample rates effectively allow the designer to ‘shape’ the distortion and noise that inevitably occurs in digital to analogue reconstruction to a frequency range that can be removed more benignly using an additional analogue low pass filter with a relatively low resonance. Low resonance generally equals less artefacts and distortions.
The CD players also tend to use a seperate digital filter… for example the CDX2 uses the PCM1704 but offloads filterering functions to the Pacific Microsonics specialed CD DSP processors.
Thanks for explaining Simon.
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