http://www.benchmarkmedia.com/sites/default/files/documents/caig.pdf
For example, they analyze the effects of different interconnect impedances and determine the optimal source impedance is in the neighborhood of 50-100 ohms. Actually 90 ohms yields the lowest peaking (most interconnect systems peak at some ultrasonic frequency; it's LCR with very low R) whereas 60 ohms yields the most extended response (from the low pass network created). Current best practice in audio is balanced interconnection, 50-100 ohms source impedance into 100k ohm load, 200khz bandwidth per component (in a multicomponent system, all the roll offs add up, so you need margin to maintain 20khz, they assume 5 analog components in series is possible), and 5v/us minimum slew rate (less than that, and you get slew rate limiting into the now pro standard +28dBu (aka 20 volts RMS) at 30kHz. (Then they laugh at adage "a system is only as good as it's weakest link", of course a real system is always *worse* than it's weakest link.)
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