No upsampling in dCS dac's, but the 5 bit Ring dac has 64x oversampling.
Indeed, but a DSD DAC is doing something remarkably similar to producing a 2MHz tone all the time. Sure the 'tone' isn't a tone, its chaotic, shaped noise but its all HF and therefore it has a high rate of change. Given its presence we need to pay serious attention to the clock to such a DAC if we don't want that HF noise to spray sidebands all over our nice low audio band noise floor.
I know Cirrus use switched caps (as do AKM who I believe are Cirrus' foundry) and so do Wolfson. I haven't seen though that ADI and BB/TI are using this approach so I wonder what their solution to it is. Of course its reduced by having more than one bit in the DAC so the out of band noise can be at a lower amplitude than the wanted signal. Clearly Bob Adams is fully aware of the issue, given his response to Dr. Hawksford. Seeing as we're on a thread about the Vivaldi, I also wonder how dCS address this issue. It doesn't look like they're using switched capacitors - they have latches and resistors. Enquiring minds would like to know...
Given the nature of the chaotic noise coming out of the modulator, I doubt very much whether conventional measurements are attuned to 'seeing' the results. Its why we need our ears to cross-check. FFTs show spurs in narrow bands but I suspect we need wavelet transforms to get a hold of the short-term changes to the (broadband) noisefloor.
I've not met either personally, but last year Scott Wurcer (on DIYA) said he'd pass on my question to Bob. I didn't get a response though - must've gotten lost in the modulation noise
I'm sorry but I don't follow this at all. You can't get LF sidebands out of the HF signal without mixing in a nonlinear system. The DS loop does do that, but the NTF suppresses it like everything else. It does not get directly translated back to baseband; the purpose of the feedback loop is to suppress that very effect.
However, you bring up an excellent point in that the HF noise (and clock) must be dealt with. It can get into everything through any number of sneaky little paths, coupled and radiated, and if coupled back to the signal can wreak havoc. Perhaps that is your point? I agree there!
It looks to me like dCS has implemented a discrete DAC using switches and resistors. I suppose we could determine if it is a ppure binary R2R or segmented by counting them, but I'm a little too lazy for that.
does it come with a free pair of binoculars so you can read the display
Wizard has recently put up two pictures of complete internal boards of the Vivaldi here : http://cybwiz.blogspot.com/2012/09/dcs-vivaldi-dac-inside.html
From a first glance it appears to shed light on a question considered earlier - why does the external clock on Vivaldi sound better? The answer appears to be that the internal clocks are on a different PCB from the ring DAC. So even the 'internal' clock appears to be compromised by having to travel from one PCB to a (presumably) adjacent one. Or am I missing something? {Ring DAC in pic 1, two oscillator modules visible in pic 2).
Yes that's how I understand it too. But since MSB is using multibit technology, the requirement for such a precise clock is not there. I suspect this clock has more placebo effect than technical effect on the output waveform.
What's the block of Lego for?
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