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Researching SD Card Transports


bobfa
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Interesting product - its worth noting that the Chinese blurb says the player needs an external 10MHz clock source to work. Which is the right-hand box in the Taobao pictures.

 

SMA cables are affordable on Taobao, under $1 for 0.5m double SMA terminated.

 

https://item.taobao.com/item.htm?spm=a230r.1.14.31.50f86ec5p1EORo&id=556991964477&ns=1&abbucket=20#detail

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Interesting indeed. I guess the yen sign is actualy Chinese currency? Approx. $ 150 in that case?

 

Can someone explain why the external 10 MHz reference clock option is not optimal? I happen to have one I do not use (Aune XC1) as it was replaced by an Afterdark Emperor Double Crown.

 

I cannot tell from the pictures whether the 10 MHz connection is 50 or 75 Ohm, anyone knows?

 

Thanks @seeteeyou for your research -- thorough as ever :-)

 

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52 minutes ago, bodiebill said:

Can someone explain why the external 10 MHz reference clock option is not optimal?

 

Given that 10MHz isn't related to either of the sample rate families (44.1kHz and 48kHz plus integer multiples), obtaining the relevant frequencies requires a phase locked loop (PLL) to be applied to the 10MHz input clock. A PLL of necessity calls for a VCO (voltage controlled oscillator) as an integral component that won't be as stable as a fixed frequency crystal. 

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7 minutes ago, opus101 said:

 

Given that 10MHz isn't related to either of the sample rate families (44.1kHz and 48kHz plus integer multiples), obtaining the relevant frequencies requires a phase locked loop (PLL) to be applied to the 10MHz input clock. A PLL of necessity calls for a VCO (voltage controlled oscillator) as an integral component that won't be as stable as a fixed frequency crystal. 

 

Thanks!

 

Does that mean that every solution with an external reference 10 MHz clock is suboptimal, even with the Mutec Ref10, Cybershaft or Afterdark clocks that people are raving about? (In my setup the Afterdark had a considerable positive impact connected to a Mutec MC-3+ USB.)

 

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I am assuming that the fixed frequency crystal oscillator isn't implemented poorly - then yes, based on my EE knowledge an external oscillator isn't going to decrease jitter compared to an XTAL sited close to the DAC chip. But then again, I might be missing something vital. In my understanding frequency references such as an external 10MHz oscillator are intended for ensuring long-term stability and accuracy rather than short-term. Long-term stability and accuracy aren't really significant issues for audio AFAIK.

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Assuming its not a placebo effect then I so far can't imagine how the short-term performance of a VCO (even a VCXO) can beat out a fixed frequency XTAL. But I'm happy if one of the vendors takes time to enlighten me.

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