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I2S: Is it a good external interconnect? Give your opinion and findings!

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Aha, I have to admit that I missed the second page of this thread & only noticed it when I got a reply to my post so apologies for having restarted what appeared to be a thread that appeared to be winding down.


Don't worry cmp, I take no offence at what you say - my skin has been thickened by posting on other more vicious forums. I read the title of the thread to mean I2S as an external interconnect (non-PC) but I can see the other interpretation.


idiot-savant, your obviously technically astute, all my stuff (is or will be) DIY so my DACs will be small boards for TDA1543, TDA1387 (an I2S version of TDA1545) & ES9018 & what you say makes sense BUT just recovering the data using a SPDIF receiver chip seems to introduce correlated jitter ala John Swenson who has done this experiment http://db.audioasylum.com/cgi/m.mpl?forum=pcaudio&n=10014&highlight=SPDIF+receiver+john+swenson&r=


Edit: Here's the more accurate post relating to what I said http://db.audioasylum.com/cgi/m.mpl?forum=pcaudio&n=647&highlight=PLL+john+swenson&r=


A thread about PLL http://www.audioasylum.com/cgi/vt.mpl?f=pcaudio&m=57592


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Right, so I see John Swenson is saying that having an SPDIF receiver active in a box corrupts another input - I don't think this is jitter, it's more likely that the SPDIF receiver is either free-running, or locked to something else - you then get cross-clock contamination. However, if the SPDIF receiver is locked to the same frequency as the DAC is ( via the wordclock via a PLL ) this will be vastly reduced...


As you're doing this as a DIY job, you can probably hand craft suitable termination between the Konnekt and your DAC using I2S, but either way your DAC is not the master. I don't know the innards of the Konnekt box to suggest any further bodgery....


your friendly neighbourhood idiot


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I think he is saying more than that:

As long as the S/PDIF receiver is in the same box, or worse, on the same board with the DAC, the correlated jitter from the PLL manages to work its way into the DAC, usually through noise on the ground connections


And this was in reply to:

The problem isn't really spdif as such, it's using a PLL to recover the clock. "All" you need to do to get around this is to put the clock in the DAC, and then send it to the PC (via an spdif xmitter, for example) and tell the PC to slave to the incoming clock. This lets the DAC run from a nice low-jitter clock right beside the chip, and the PC which really doesn't care much for what clock it uses (for audio-only anyway) is perfectly happy slaving from say an incoming spdif signal.


So using a SPDIF receiver seems to be sub-optimal!


My TDA DACs are ones I have in my box - the 32bit Sabre I bought & intend to implement it soon. EVEN with the superior SPDIF handling of the Sabre it's reported that I2S input sounds better than S/PDIF


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If you can't make the Konnekt slave to your DAC ( which would involve surgery on the Konnekt ) everything else is a compromise.


I think that if your DAC is a distance away ( say a foot or so ), the amount of overall jitter you will get from SPDIF & PLL will be much lower than using I2S but what you do have will be more correlated jitter.


As a DIY'er, you're going to have to make the decision, which is the beauty of DIY.


If it were me, I'd either modify the Konnekt, get an FPGA development board, or use an SPDIF receiver + PLL...


your friendly neighbourhood idiot


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