It's interesting to look at the workings of Nagra HD DAC
From HiFi+ review:
"The audiophile intent begins after these balancing operations, however. As suggested previously, the company went right back to first principles. Nagra sees the quantization noise of 16‑bit/44.1kHz digital audio, and the methods used to quell that noise, as one of the big problems of the CD age. Crude brickwall filters that block out any noise above 22.1kHz can undermine phase above 10kHz, the company suggests, while conventional oversampling and interpolation methods are a cure that Nagra believes is often worse than the disease.
Nagra instead concentrated on the goals of getting the extraction and converting of data absolutely right, without resorting to ‘cheating’ (oversampling). Ultimately, this led to Direct Stream Digital, and Nagra (in association with DSD pioneer Andreas Koch) developed its own Sigma‑Delta DSD processing, on a custom 72‑bit Field Programmable Gate Array. Add to that a custom time-correction algorithm, in place of the usual demands for atomic clocks at this grade, to keep this DAC temporally precise, and the result is the removal of that quantization noise up to so far beyond the audio band, its impact is effectively completely eliminated."
Nagra avoided super clocks, used FPGA, special algorithm for time correction.".........remind you of any other DACs?
It converts everything to DSD though. I would be surprised if it will match DAVE for musicality.
Sorry, but I don't usually comment of other companies products, but the statement that this reminds you of other DAC's (Dave) really raised my blood pressure.
Lets look at each statement in turn:
"Nagra sees the quantization noise of 16‑bit/44.1kHz digital audio, and the methods used to quell that noise"
There is absolutely no problem with quantization noise, if correctly done, as it adds a fixed unvarying noise. Because it is unvarying, it has no consequence on the brains ability to separate instruments, define placement in the sound stage, determine timbre and transients and so has no effect on musicality (that is the ability to enjoy music emotionally).
The scary thing is the statement "methods use to quell that noise". What on earth does that mean? The dither is part of the recording, and applied in the analogue domain, so it is the actual signal you want to reproduce. Nobody quells that noise, as how do you separate it from the intended signal?
"Crude brickwall filters that block out any noise above 22.1kHz can undermine phase above 10kHz"
A brickwall filter is an FIR symmetric filter and these are guaranteed to be linear phase, so this statement is just plain wrong.
"while conventional oversampling and interpolation methods are a cure that Nagra believes is often worse than the disease."
What are they saying here? NOS? That topology creates enormous timing errors, and that is the complete opposite with what I do.
"Nagra instead concentrated on the goals of getting the extraction and converting of data absolutely right, without resorting to ‘cheating’ (oversampling)."
Again completely diametrically opposed to what I say. The job of a DAC is NOT to reproduce the digital data, but to reproduce the analogue bandwidth limited signal at the point it is sampled in the ADC. To perfectly create the analogue signal in the digital domain requires infinite oversampling. This is also the only way to reduce jitter sensitivity, and eliminate noise floor modulation, an effect for which the brain is extremely sensitive to. You absolutely can't refer to oversampling as cheating, as it gets the signal much closer to the original analogue signal. But of course, if your intention is to create distortion and noise, then by all means refer to oversampling as cheating, as it won't allow you to achieve your goal of more distortion and noise floor modulation.
"Add to that a custom time-correction algorithm, in place of the usual demands for atomic clocks at this grade, to keep this DAC temporally precise"
Confusing two separate and independent things. The interpolation filter algorithm (if that's what they are talking about) can not change the requirements for the master clock, which depends principally upon the DAC topology.
"and the result is the removal of that quantization noise up to so far beyond the audio band, its impact is effectively completely eliminated"
The quantization noise of 16‑bit/44.1kHz digital audio? That won't get touched at all by any such process. Are they talking about the quantization noise from the noise shaper? In which case don't use DSD, oversample at high rates, and run the noise shaper with n bit quantizer also at high rates (like my 2048 FS). DSD at 128 FS creates vast amounts of out of band noise with typically -20dB down at 200 kHz. You can never refer to noise at 200 kHz at -20dB as "its impact is effectively completely eliminated."
And yes, my previous posting recently confirmed that it was impossible to properly reproduce depth using DSD, as the noise shaper resolution is inadequate. Dave has noise shapers with a trillion times more resolution than traditional DSD noise shapers.
So no, this DAC bears absolutely no similarity with my work - it may have FPGA's, and not use atomic clocks, but that's the only similarity.
Rob
