Quality of digital cable from from source to DAC?

Then perhaps this is central to my lack of understanding. Are not the electromagnetic waves by which the data is being transferred thru the cables between the router/streamer and streamer/DAC purely digital (packets of ones and zeros) in form?

Nothing should be analog until the Digital Analog Convertor converts it, right? Or am I not understanding this (or it's implications) correctly?
Todd

Thanks everyone for your time and effort given.

Twoleftears, waded thru some of the silver/copper discussion and remain perplexed (as I believe was your intent to display I am certainly not alone) that little mention was made to the differences (if any do exist?) in the movement of digital signals vs. analog signals.   
Wow Mitch, thanks for your input and effort with all the relative links. No doubt to be intriguing reads.

I will be letting my ears and wallet that will determine MY take on this. Am comfortable knowing that some things in life (for which this may be another instance) simply defy explanation. But my desire to have understanding of most things is strong, particularly when they effect both my happiness and my wallet. Wish it were easier to do some blind-tested cable swapping myself, but for numerous reasons this is not likely to ever happen. Too many hobbies and desires. So just trying/hoping to make the best out of learning thru others reported efforts and experiences.  

Have had opportunity to acquire several credit hours of physics, thermodynamics, etc. in my earlier years. While I can't necessarily hold an in-depth conversation on ALL the various aspects involved as electricity passes thru metal, I do have at least a little understanding of that physical process and many of the factors/elements that might affect it.

Hoping some of the links offered might delve into the differences (if they exist?) between the movement of digital data vs. analog data thru metal cable runs. This I have little to no understanding of.   

Thanks again to everyone's input.

kijanki, your's is one of most thorough explanations I've encountered. Thanks for that effort. Occasionally do some sea kayaking. There are seemingly always some occasions where, due to any number of factors (i.e. changing wind speed, water depth, shore reflections, etc.) that what are typically dependable and predictable wave movements become what are referred to as 'confused waves'. Guessing on a micro-scale, much the same applies with electrons in a sea of copper wire. Sorry, I live by association. Don't know that it's an accurate correlation, but seems like maybe it ought to be?
andy2, please note this is in NO way a challenge to what you say, but simply for me to express my lack of understanding. '2. It's electrical signals' I totally get. What I question (because I have NO idea) is that are they two different 'ways' (for lack of better word) that the electrical signals are transferring information?

My perception (and this is what I'm SO hoping to clean up) is that the source (server/cd/whatever) transferring the data of a 'digital' file by emitting electrical signals in simple (relative to analog), concise, rigidly defined, regulated pulses (the ones and zeros) are painting a complex (understatement) 'coded' picture (maybe movie's the better term, as it's constantly changing?) that the DAC must decode and translate into an analog electrical signal.

The electronic 'digital' signal carrying this coded information deviates little to none (I would think?) in amplitude or frequency. The electronic signal (pulse) is either go, or no go, yes or no, (1 or 0), and sequenced to relay a defined coded message that the DAC can interpolate. Given the velocity of an electrical wave through a copper (or silver)  wire is deemed to be roughly 90% the speed of light, essentially instantaneous relative to the lengths of cables in our systems, seems that 1. deviations in the devices 'clocking' mechanism or 2. potential electromagnetic interference from surrounding electronic wave movement could really be the only sources to alter the passage of this data transfer through a wire.    

Electronic signals transferring analog information (I would think) are another animal altogether, deviating in both frequency and amplitude, and in turn being more more complex signal transfer that would be susceptible to alteration (error) in part due to its complexity. 

With this point of view (wrong as it likely is), seems that other than obtaining the best possible shielding there would be little to gain relative to different cables in transferring digital (coded) information, where as with the complexity of an analog electronic signal would actually benefit from a transducer that imposed as few impediments as possible to the electrons path.    

Well aware this is absurdly simplistic in (my) thought and supremely complex in reality. And I reiterate for any one reading what I've written, this in all likelihood IS NOT how things really work, again, it's only my perception. Not all that bright here, but smart enough to know it's likely way off in reality...
Came across an 'jitter' article that seems both broad and approachable (for us not so technically aware), in case anyone's interested:
http://www.enjoythemusic.com/magazine/manufacture/0509/
Not asking that anyone write a dissertation to cleanse my ignorance to the matter, but if anyone can at least guide me towards some reading that might enlighten me in my quest to (at least sort'a) know how it really works, will be much appreciated.
Todd