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23 hours ago, Confused said:

Another thought here.  If the sMS-200Ultra is simply a sMS-200 with a better clock, then I would have thought a sMS-200 (not Ultra) with the external clock mod would be all you need?

 

The short answer is, it's complicated. 

 

Clocks have to be placed as close to the DAC as possible. This is because the jitter performance suffers the more interfaces get in the way. If you had clocks with equal performance, the clock placed next to the DAC will perform better than the same clock placed externally. 

 

Furthermore, the performance of the external clock depends on the type of PLL (phase lock loop) in your DAC. 

 

Using an external clock may or may not increase the performance of your DAC. It comes down to the performance of the external clock, the performance of the clock in your DAC, the design of the PLL, the number of interfaces the external clock has to traverse, and even the quality of the cable connecting the external clock to your DAC*. 

 

(* this is something that even objectivists won't disagree with! It needs to be 75 Ohm impedance, and both clock output and DAC clock input need to be designed within spec, otherwise jitter performance suffers) 

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What I am saying is that the clock signal generator has to be as close to the DAC chip as possible. This is why the clock which is built into your DAC has an inherent advantage over any external clock. For an external clock to offer superior performance depends on the combination of factors that I listed. 

 

Note that I am careful to say that the external clock will or won't offer a performance advantage. It might, but it is not possible to make a blanket statement. Unless you happen to be John Swenson and have access to equipment that can measure this amount of jitter, you will not be able to tell the difference an external clock makes (either positive or negative), short of using your ears and deciding if it sounds better or not. 

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Appreciate your contribution to this thread, Julian. 

 

I would also suggest that any potential purchaser of your clock check their DAC to see if it accepts a 10MHz input. My DAC for example (Merging NADAC) only accepts inputs in the base frequency or multiples thereof - e.g. 44.1kHz, 48kHz, etc. I understand (correct me if i'm wrong) that the Mutec does not have a synthesizer and is therefore unable to generate 44.1kHz for my DAC? 

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  • 2 weeks later...
1 hour ago, JohnSwenson said:

If the source board design and layout, cable, receiver board design and layout are all at the same impedance this will not be a problem. BUT the practice of unsoldering an oscillator from a board and soldering some coax to the pads is almost going to guarantee that you have a massive impedance mismatch, meaning you WILL have cable length issues, but it is almost impossible to figure out in advance what they might be. Again it may cause a problem, it may not.

 

 

Interesting discussion, thank you everyone. That SOTM sCLK-EX board recommends desoldering the oscillator, which as you say, will cause a massive impedance mismatch which may or may not make cable length critical. Given that the SOTM board is meant to be mounted in a 3.5" bay within the PC, won't this mean that the cable lengths will be very short, which would reduce the effect of cable length? 

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