Transport signal thru mult cables simultaneously?


So I want to break-in two digital cables at the same time; one AES/EBU and one SE. I have the AES/EBU in input one on my DAC and the SE in input 2. Does signal pass through both cables regardless of which input I'm listening thru or does only the cable which is plugged into the engaged input receive signal? Doesn't the transport output signal thru all cables which are plugged into its output jacks; or does the circut open on the cable which is plugged into the non-engaged input such that the signal does not pass thru it? Bottom-line: Can you break-in two digital cables simultaneously using the same transport/DAC?
stew3859
Can you break-in two digital cables simultaneously using the same transport/DAC?
Yes.

All that is required for normal current to flow through each cable is the presence of the termination resistor (or equivalent load impedance) in the corresponding input circuit of the DAC (75 ohms for S/PDIF, 110 ohms for AES/EBU). I can't envision a DAC design that would remove the termination from the unselected input, in part because the terminations and receiver circuits are separate and different for the two inputs. And as long as the termination is present, the transport would have no way of knowing which DAC input is selected (assuming the transport itself does not have a switch to select which of its outputs is used).

Disclaimer: This response does not imply an opinion as to whether or not the breakin process will accomplish anything.

Regards,
-- Al
Al:
Thanks for the thoughtful response. Much appreciated.
Al, is this because you do not have an opinion regarding breaki-in of cables in general, or only for digital cables?
KN -- My statement about not having an opinion pertained to digital cables specifically. With respect to cables in general, I believe that breakin effects can be and in many cases are significant. However I also suspect that there are a lot of cases in which audiophiles misattribute perceived changes to cable breakin effects. Those changes actually being caused by things like ongoing aging or breakin of system components, changes in AC line voltage or noise conditions, even changes in temperature or humidity. (Humidity, for example, can have profound effects on electrostatic speakers). Not to mention the vagaries of aural memory.

Regards,
-- Al
Thanks, helpful. Do you have any thoughts on the relative importance of break-in for digital vs analog cables, based on theory, experience or other reference? I have read in several threads here about people breaking-in their digital cables, and I have wondered about the need for that. I guess if break-in is a real phenomena of changing how a signal interacts with the surrounding dielectric, then any signal could be affected.

kn
KN, no, I really don't have any particular thoughts about the importance of break-in for digital cables. I'll say, though, that I would not consider anecdotal reports of such experiences to be definitive unless they involved direct comparison on the same day of a broken in cable and an identical cable that was not broken in. With the system being in an equal state of warmup in both cases.

And even then I would be uncertain as to how applicable the reported experience would be to other digital cables connecting other digital components.

Regards,
-- Al
A further thought that occurs to me regarding digital cable break-in: Since S/PDIF and AES/EBU cables will be terminated in nominal impedances of 75 ohms and 110 ohms, respectively, while line-level analog interconnects will generally be terminated in tens of thousands of ohms, and the signal amplitudes involved in each of those cases are not greatly dissimilar, in normal use vastly more current will be flowing in a digital cable than in an analog line level interconnect.

Therefore whatever break-in effects may occur in a digital cable, if any, will tend to happen far more quickly in normal use than would be the case with analog interconnects.

Regards,
-- Al
Interesting, as usual Al. Thanks

kn