...when you say "keep the volume on the computer wide open" do you mean full volume?
Yes.
...when you say "it is essentially out of the signal path", does that mean that at full volume, the circuitry in the computer is not processing the signal, while at lower volumes the signal is processed in such a way that somehow degrades it?
Yes. Regardless of whether a volume control is inserted into an analog or digital signal path, when it is wide open and not attenuating the signal, its sonic degradation is minimized.
...I don't really know what "electronic volume control" means and what other type of volume control(s) it is distinct from, since I think of all my stereo components as electronic equipment. What is an electronic volume control and how does it affect the signal?
An electronic volume control is usually an IC (integrated circuit). An analog volume control is usually a rotary control that varies in electrical resistance as it is rotated. A more sophisticated version of an analog volume control is a
precision stepped attenuator, which is a rotary switch with more than twenty positions, which in every position except for wide open, feeds the signal through a particular value of resistor.
Finally, I'm curious if there's any advantage (in keeping the signal clean) to buying a single cable with the mini stereo plug on one end and the RCA connectors on the other, rather than using an adapter with a set of RCA cables and having one more connection point that the signal has to jump across.
Doing it that way limits you to using the interconnect cables that are wired to the adapter, rather than being able to use audiophile-grade interconnects.
Any time an audio signal is manipulated in any way, some distortion of the original signal is inevitable. The audio signal coming out of your Mac's headphone jack is equivalent to the pure water in the stream at the top of the mountain. We want to keep the signal path as simple as possible to minimize the distortion that's added to it.
