I don't know about audio DAC chip which would not do it in 2 stages. The difrerence between these stages is that the first one is filtered (these digital filters are often user selectable) and the 2nd interpolation stage is simplified without proper filtering. 705.6/768k was used only as an example, with ESS chips it is probably higher. It may also depend on input signal sample rate. I mentioned 10MHz as an approximate value of typical modulator rate. There are more frequencies at which delta sigma modulator can operate. Details can be found in documentation which is available for developers.How do you know there are two stages oversampling on this dac? First at 705.6/768k and the second at which frequency? You mentioned about 10 Mhz earlier.
On ESS chips: With DSD input you skip complete oversampling (both stages). DSD signal then goes through digital volume control to delta sigma modulator input. Input signal rate for example 22.57 MHz is not changed during volume processing. So delta sigma modulator will operate on 22.57 MHz and its output is filtered by D/A stage. It works so on each input DSD rate starting from 2.8 MHz. Modulator operating rate is adapted to input DSD signal rate.In case of choosing PCM to DSD upsampling, would it be better or more close to 'second stage' than the former?
If this dac plays native DSD512 at 44.1Khz, which is 22.57 Mhz according to an earlier post, this frequency is higher than 10 Mhz, so does DSD do a second stage aswell?
With other chips, if you use the so called direct DSD path (which is not available for ESS DACs), you skip also the delta sigma modulator (DSD signal is already modulated) so the DSD signal comes directly to D/A stage, skipping complete digital processing, which is in action with PCM input. DAC volume control is not possible with direct DSD path.
By the way, volume control for DSD file playback is not available in usual software players too, because they don't know to perform DSP on DSD content. The exception is HQPlayer, which is able of volume control, parametric equalization, convolution and rate conversion also with DSD content without any intermediate conversion to PCM.
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