I think it's clear from the entirety of this discussion that each system requires its own unique treatments in terms of electrical and mechanical conditions. However, I do agree that there are some activities which will transcend the individuality of the system, and be virtually universal in their behavior.
#1 - Make sure your power is clean, and constant, regardless of the methods used to achieve that.
#2 - Reduce stray hum, RFI, and EMI fields surrounding your equipment, and block, or otherwise deter these fields from affecting your equipment, including cables.
#3 - Consider your equipment and cables to be "vibration antennas" and attempt to reduce, or control, the mechanical resonances that may be induced by external sources. Attempts to control inherent, natural resonant frequencies can be counterproductive.
#4 - Remember that all signal carrying wires have an inductive field around them that is actually a part of the signal. Attempts to suppress this will affect the quality of the signal in the wire. Allowing these unsuppressed fields to interact with other unsuppressed signal carrying wires could be detrimental to sound.
#5 - Place transformers and other large magnetic field generating devices far enough away from sensitive items which may be influenced by the fields.
#6 - Just because it may be difficult/expensive to do something behind the wall does not mean that you may not reap improvements from these efforts. It is a known fact the the Romex moves enough from its own movement inside the wall, that it can cause a connection to sever from metal fatique, and this is why the Romex is to be stapled within several inches of the rough-in box. We haven't even discussed whether the conductive staples on the Romex could be a factor, when these are plentiful, and in direct contact with the Romex sheath, and even pinching the wire in some cases. Maybe non-conductive staples may play a part. Maybe distance between staples may have some electrical or mechanical effect.
#7 - Make good, clean connections wherever any connection is to be made, and periodically clean them. Including in the outlet boxes, and breakers.
#8 - Use good grounding tecniques.
#9 - If power conditioning is required in your area, due to grungy power from the street at varying times of day, use it.
#10 - Use your ears to decide the value of the modification.
#1 - Make sure your power is clean, and constant, regardless of the methods used to achieve that.
#2 - Reduce stray hum, RFI, and EMI fields surrounding your equipment, and block, or otherwise deter these fields from affecting your equipment, including cables.
#3 - Consider your equipment and cables to be "vibration antennas" and attempt to reduce, or control, the mechanical resonances that may be induced by external sources. Attempts to control inherent, natural resonant frequencies can be counterproductive.
#4 - Remember that all signal carrying wires have an inductive field around them that is actually a part of the signal. Attempts to suppress this will affect the quality of the signal in the wire. Allowing these unsuppressed fields to interact with other unsuppressed signal carrying wires could be detrimental to sound.
#5 - Place transformers and other large magnetic field generating devices far enough away from sensitive items which may be influenced by the fields.
#6 - Just because it may be difficult/expensive to do something behind the wall does not mean that you may not reap improvements from these efforts. It is a known fact the the Romex moves enough from its own movement inside the wall, that it can cause a connection to sever from metal fatique, and this is why the Romex is to be stapled within several inches of the rough-in box. We haven't even discussed whether the conductive staples on the Romex could be a factor, when these are plentiful, and in direct contact with the Romex sheath, and even pinching the wire in some cases. Maybe non-conductive staples may play a part. Maybe distance between staples may have some electrical or mechanical effect.
#7 - Make good, clean connections wherever any connection is to be made, and periodically clean them. Including in the outlet boxes, and breakers.
#8 - Use good grounding tecniques.
#9 - If power conditioning is required in your area, due to grungy power from the street at varying times of day, use it.
#10 - Use your ears to decide the value of the modification.