Transport signal thru mult cables simultaneously?

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