It's not as simple as just connecting two components with lamp cord wire. Or any other simple twisted pair of conductors. Ironically this method while primitive and least complex is also the most colored with the highest level of all sorts of distortion. Interface. Interface. Interface. The three I's. Or I cubed. Have you peeps ever seen an HDMI interface? Care to guess how many transistors make up that circuit? USB? Firewire? ESATA? What about basic digital audio with multiple buffers and clocks, etc.?
How about precision test equipment? Aerospace? Defense? Anything military? 50 Ohm interface is very popular in these fields. Even an oscilloscope has an interface. Come to think of it, outside of a light bulb and a washing machine, everything else has some sort of proper termination, either with specific geometry of the cable or connector itself, or a full blown circuit. Component video, S-video, digital coax, optical, RF, antenna, locators, instrumentation, computers, guidance, radio, radars, neutron bomb triggers... Yup, you guessed it. Everything works on proper impedance matching and termination.
So why not audio? Have any of you actually used a basic Tektronix to see what is going on at the output of an audio amplifier? There's all sorts of garbage way up into the megahertz region. Complex harmonics due to signal (music), RF, reflections, etc. And it doesn't help that the speakers have a variable impedance which is frequency related. The amps have a 0 Ohm output. Preamps have a 1K Ohm output. The amps have a 10K Ohm input. In other words, what a mess and a giant pile of crap.
Most of you can decrease your amplifier's distortion by simply installing a low pass filter. I recommend ya'll try a 10uH inductor in series with the speakers. And then measure the amplifier's various distortion levels. 10uH inductor driving a tweeter with a nominal impedance of 3-4 Ohms, the corner frequency is way past what the human ear can hear. Yet the effects are very audible. Why? That's the problem with armchair experts. Remember what Indiana Jones told that kid at the library? Put that book down and go experience the world first hand. You peeps hiding behind your computer monitors should do some first hand experimentation. These parts cost pennies.
Take a 75 Ohm coax cable. Measure jitter with BNC connectors. Now repeat with RCA connectors. Due to the space between the center pin and the outer ring, no RCA connector can ever be a true 75 Ohm part. You will notice reflections. Higher jitter. This can be fixed by installing a 75 Ohm resistor at the source end. Or a 1-5 Ohm resistor at each end. Now do the same test with length. Due to transmission line effects a 1 meter cable will have higher jitter than a 1.5 meter cable. You can further lower jitter and RF noise with a 100pF parallel capacitor.
The possibilities are endless. We haven't even scratched the surface of electronic science. It's fun and rewarding to do these tests and measurements followed by listening sessions. To see true results first hand and to hear them.