[Robert Peirce]

Well, after much listening, I have concluded that a 25-30' length of
Toslink may be about the same as a 25-30' length of wire, at least as
far as I will be able to tell.

This raises another interesting point. How will it compare to what I
have now? The source and the DAC are constants. So everything depends
on the connection.

At present, I use ethernet over powerline because my WiFi signal isn't
strong enough to the area where my stereo is located. I use Airfoil to
transmit the signal over ethernet. It uses Apple's Core Audio. An
ethernet cable goes from my MacBook Pro to a powerline adaptor. Another
powerline adaptor feeds my AppleTV and the AppleTV feeds the DAC over a
short TosLink cable. This is a dedicated circuit. It is only used for
audio.

The proposed setup is to run a 25-30' Toslink cable directly from the
MacBook Pro's optical output to the DAC. The optical output also uses
Apple's Core Audio but possibly not in the same way. Airfoil would not
be needed.

I suspect there are audible differences between the two setups. The
important point is will I be able to hear them and if so, which will be
better? Generally, I have found the less hardware in the circuit the
less chance of audible conflicts. Nevertheless, regardless of any
theoretical difference, I suspect I won't hear any real difference.
However, I don't know.