It has become quite common in high-end audiophile circles to go all “analog” on parts of the signal path that are carrying digital information. Talking about noise or electrical interference in a USB cable as it carries electrical signals from the output of your computer to the input of your DAC, ignores the basic tenants of digital representations of music or images or video or anything else. I’m not sure how this “analog” thinking crept into the land of computer audio but it seems to have taken a strong hold in some circles.
There some very experienced and knowledgeable electrical engineers out there explaining how electrical signals pollute digital streams or packets of digital media and others with equal experience and knowledge that dismiss the claimed issues of noise in the outputs of their DACs. Who’s right? You have to go back to the basics of digital coding to begin to grasp both sides of this issue. And while I used to build Heathkits, know how to read a schematic, and spent 5 years making a living as an electronics repairman, my knowledge is insufficient to parse through all of the finer points of the processes involved…but as an audio engineer and musician, I can share my experience and knowledge. I teach digital audio to a new group of audio engineering students every fall. I do know some things.
There may be an infinite number of voltage levels tripping through a circuit board, USB cable, Ethernet cable, or DAC…the digital information doesn’t care. The process of converting or representing an analog electrical signal in simple binary…ones and zeros…bits only needs to know if the lights are on or off? That’s the beauty of digital. John Swenson, an engineer interviewed over at Audiostream.com stated, “… the wire can pick up huge amounts of noise and still be ‘read’ properly. This is the promise of digital and why it is used in the first place.” Let’s be clear about what he’s saying. The room in which you’re processing two states…binary data or lights on or light off…can be filled with smoke, have a large number of bouncing ping pong balls obscuring the space, or have dim lights or bright lights…all the digital receiver (in this case you!) has to be able to perceive is whether the lights are on or are they off.
I’m going to ignore the issue of sampling rate and jitter because a good quality DAC takes care of reclocking…it’s only the data that matters.
I’ve repeated my mantra on the “bits are bits” debate. If a successful transmission of digital data can be accomplished by a reasonable quality USB or Ethernet cable or by a WiFi connection, the medium doesn’t have any chance of impacting the fidelity of the reproduced sound. Of course, this will only be the case if the reconstruction of the waveform is done by the same DAC. Naturally, different DACs from different designers will have their own sonic signatures.
Why do I get so righteous about this rather simple concept? Because I’ve done repeated tests on cables and discs…expensive or treated or not…and found that the digital bits from one path vs. a challenging path when compared using polarity reversal results in a complete null signal. If they perfectly null each other then they were identical. And even the most ardent “bits are NOT bits” person has a very hard time explaining how things can sound different between two sets of data that are identical.
That doesn’t mean they won’t keep trying.