Digital coaxial audio cable suggestions.

1.5 will work ok, but i will have to coil it up at one end. So what to buy and from where? $200 or so, good quality and sound, flexible and well shielded from RF.

Kijanki:
Would that also apply for a word clock cable. I have a Esoteric player that accepts a 10mhz signal and I'm running a 3m length BNC-BNC 75ohm digital cable from the external word clock?.

Thanks.

06-13-12: Mike60
What happens when you have reflections? What do you hear?

There would be an increase in jitter. See this paper for further background on jitter. The degree to which the jitter would have audible consequences is dependent on the particular components. In some cases there may be little or no consequence, depending on the jitter rejection capability of the DAC and other factors.

Typically, though, there would be a general loss of clarity and focus, its exact character depending on the spectral characteristics (frequency content) of the jitter, which in turn are dependent in unpredictable ways on the particular components and setup.

06-13-12: Flashunlock
Would that also apply for a word clock cable. I have a Esoteric player that accepts a 10mhz signal and I'm running a 3m length BNC-BNC 75ohm digital cable from the external word clock?.

I suspect that the risetime and falltime of the 10 MHz signal that is being sent out by whatever is generating your word clock are significantly faster than the risetime and falltime of the S/PDIF output of a typical transport or other S/PDIF source, so it is a fundamentally different situation.

Also, the problem that can occur for S/PDIF with a 1 meter length will be avoided by lengths that are longer than 1.5 meters, as long as the length is not so long that reflections corresponding to one signal edge arrive near the mid-point of the NEXT signal edge, or some other subsequent edge. 3 meters is too short to cause a problem on the "next" edge of a 10 MHz square wave, and is very unlikely to affect subsequent edges, in part because those edges would only be affected by reflections making multiple round-trips (i.e., reflecting and re-reflecting multiple times between the two components), which would cause them to be very small in amplitude.

That said, when possible it is preferable to avoid longer lengths like that, because it will reduce the possibility that jitter may occur as a result of ground loop-related noise or rfi/emi pickup.

Regards,
-- Al

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.