Digital coaxial audio cable suggestions.


Suggestions for a reasonably flexible 1m long digital coaxial cable for around $200 that is well shielded from RF and sounds good? Also, where can I reliably buy the suggested cable from?
mike60
Mike60, Get 1.5m Reflections come from change in characteristic impedance that for higher frequencies can be defined as SQRT(L/C) and depends on geometry of the cable or connector (for given dielectric type). When you have absolutely perfect cables there would be no reflections but in practice it is almost impossible. Reflections contaminate straight transition edge of digital signal changing time when threshold is crossed (level recognized) making signal to jitter in time. This jitter is a form of modulation and as such makes two sidebands in frequency domain. These sidebands are very small but audible because not harmonically related to root frequency. With complex signal containing many frequencies (music) it creates many sidebands that together become hash/noise. This noise amplitude is proportional to signal amplitude and is zero when music is not playing - difficult to detect. It appears as lack of clarity and affects even imaging. Some of this jitter comes from noise (ambient or system) and is correlated but some is random. Using impedance matched and well shielded cables plus providing clean power reduces jitter effects.
Noisy system modulates amplitude of transmitted signal but also makes threshold (level recognition point) on receiver side not steady causing jitter.

It is very difficult to predict how reflections affect the signal because reflected signal bounces back and forth like echo between walls but there are ways of predicting how signal will get modified (Bergerone Diagrams). Read more here: http://pages.infinit.net/alcor/docs/math/TRANSMISSION%20LINE%20EFFECTS%20%20version%20L.pdf

Flashunlock, I'm not familiar with Esoteric separate clock signal but I would clock the source from the DAC, using buffered clock, on opposite edges to active clock edge (source placing bit of data on falling edge and DAC clocking it on rising edge). It is typical synchronous transmission (vs asynchronous S/Pdif) less susceptible to cable jitter but still susceptible to receiver (DAC) system noise induced jitter. I assume that Esoteric has something like that.
Al is absolutely right stressing importance of keeping cables short. Non-magnetic shield does not stop EMI (for instance radio waves) but induced noise travels on the outside of the cable (shield) to ground because of the skin effect. Skin effect does not work at lower frequency EMI but cable is not long enough to become antenna (1/10 of wavelength) unless you make it longer than necessary. In addition, since induced noise returns thru the shield it causes voltage drops visible as signal when shield is used as one conductor (S/Pdif). Longer shield means higher impedance and bigger voltage drops.
As usual, fantastic explanations from Al and Kijanki.
06-13-12: Mike60
What happens when you have reflections? What do you hear?
As Al mentioned, it's difficult to predict the exact audible effects of jitter for any particular system, though there do seem to be some typical effects.

I've had several opportunities to hear the effects of jitter in my system. A couple years ago, I added a reclocker (its raison d'ĂȘtre is to reduce jitter). Once or twice I reduced jitter accidentally, like when I replaced an unshielded ethernet cable with a shielded one. IME, hearing jitter is something that only happens when you REDUCE it. Anyway, here are some of its audible effects...

1. Reduced resolution
2. Shrillness in the highs
3. Fuzzy imaging
4. Unrealistic instrument timbres
5. Lack of pitch definition in the bass

I'm sure there are more effects, but those are the ones I've noticed in my system that I've attributed to jitter. Taken together, reducing jitter results in a sound that is less "digital."

Hope that helps.

Bryon
I bought the DH Labs D-75 a few months ago and have been very happy with it. Great cable, great company. I was using a pure silver cable before and haven't felt the need to put it back in...yet.
I agree with the recommendation for the DH Labs Silver Sonic D-75.

An internet search will pull up several online dealers, including at least one who advertises here. You also can email DH Labs at info@silversonic.com for the nearest dealer.