Digital Cables

These are situations for which the impact of EMI/RFI on the digital conversion process will be audible if error recovery is not instantaneous as well as potential impacts on analog output stages. 

The following digital impacts (#1 and #3) are errors in digital-to-analog conversion, not in transferring bits for which any errors can be resolved with error checking and a buffer. A buffer doesn't help in these situations because EMI/RFI is affecting the validity of the output from the digital-to-analog conversion process.

1. Clock Instability creating Jitter

• How it happens: EMI/RFI couples into the DAC’s master clock circuit, nudging the timing of when each sample is converted.

• Effect on conversion: The DAC still outputs the correct voltage levels, but at slightly the wrong instants in time.

• Audible impact: Treble glare or “etchiness”, Flattened stereo image, Loss of spaciousness

2. Coupling into the Analog Output Stage

• How it happens: After the DAC chip outputs a small analog voltage, it’s sent through op-amps or discrete analog stages. These are high-gain, wide-bandwidth circuits — practically antennas for EMI/RFI.

• Effect on conversion: Adds a noise floor “haze”, Can cause intermodulation distortion (high-frequency interference folding down into the audible band)

• Audible impact: Graininess, Fatigue in longer listening sessions, Reduced warmth and realism

3. Reference Voltage Pollution

• How it happens: Every DAC chip uses a precise voltage reference to decide, for example, “this bit pattern equals 0.734 V.” EMI/RFI sneaking in via the power supply or ground can modulate this reference.

• Effect on conversion: The DAC’s internal scale is wobbling, so each sample isn’t output at the exact intended level.

• Audible impact: Subtle distortion, Loss of microdetail, “Gray” or veiled background instead of black silence

@calvinandhobbes Very Interesting indeed! Thank you!! 

@calvinandhobbes +1 

Both analog & digital signals may be contaminated by - conducted EMI and radiated EMI.   In a resolving system, when the noise is mitigated, the clarity of tone & timbre is revealed.    The harshness is gone.   It takes time & effort to clean it up.

- - - 

My experience with EMI at the digital streaming front end.

My experience with EMI behind the equipment rack.

@steakster Are you saying that the wi-fi data that my Node N130 is getting from my router (wi-fi not ethernet) carries EMI contamination from the router? 

I hooked up my DAC from my bridge with a standard (stock?) cable of each type, to listen for a format winner.

At first, coaxial was beating the newer I2S over HDMI for me, because the skinny little HDMI data cable was unable to carry any weight, which IS particularly bad for heavy metal fans.  After that, however, since the data lane was un-shared, my data now came through clear and with more agility because of it.  Also, the soundstage became tight and natural.  It sounded like I upgraded to a 4 lane roadway, for sure, it’s just for that skinny little HDMI lane size.  A XLR + COAX I2S connection is the connection that would beat all others at everything, thanks to 4 lanes, and an extra fat one for the dedicated data lane, that way.

So now, I2S over HDMI is the only connection that doesn’t sound automatically wrong.  I upgraded the cable to a Nordost Blue Heaven HDMI cable, and my improvement made me think it was still only the digital, except then that’s while it’s everything too, so that’s not necessarily bad.  I got a bit more speed and tonality out of it, but it was still actually kind of a disappointment.  Probably because nothing but lane gauge can bring back my weight.  Its still a bit more organic sounding, and that earliness helps all the way up the chain, so I would upgrade again, just maybe to a better copper one instead of expensive (but still only 99.99%) silver.  The USB cable in front of my bridge wasn’t much of a big deal, even at $150, so I should be looking at a Supra, until my budget is ready for better USB some more, but only after 4 more power cables that otherwise won’t come until always after something else.  It’s ok, I’ve learned that power cables help a lot too, so that’s my weak link for a while.

But yeah, the OP’s question’s answer should be torn between the digital cable being most important, since it comes so early, except that also it’s still only the digital cable, and all cables could be making your chained system perform better, with upgrades.  There is a $23k power cable that people say beats all the rest.  Remember that a wealthy you could just buy that cable for everything you have also, and then tell you that your gear isn’t doing what it could actually be doing without that power cable on it.  You wouldn’t be wrong, either, it’s just probably more "sorry about your wallet" for you than if you get to him, so far.

Thanks everyone, for sharing your specific cable experiences.

Edit: Oh right, the digital connection difference topic thread.  Then again the part where I2S needs to switch to XLR + COAX for it’s 4 wires, including the big fat COAX data cable we got from Sony/Phillips, that carries weight, especially for the sake of heavy metal fans, except now that it’s cleared up of sharing traffic with 3 other lanes, it has all the agility and clarity we at least still get from HDMI, to keep I2S from grudgingly being on top of digital transmission.  My sub especially is doing nothing since I2S over HDMI, it’s just that now it’s like my sub is the next model up at it, only with less of that to do, especially HDMI doesn't do trailing ends of weighty sounds VS COAX.