The main important first knowledge fact in audio life is this one, some of us learned the hard way:
Past some point in technological electronic engineering improvement in the past collective or personal history, the main improvement coming from an audio system, come less from an electronical design new progress than from an improved control of the mechanical, electrical and acoustical embeddings of the audio system...
Most embeddings controls are often simple devices and also sometimes simple advices (speakers positioning) and play now the first role in the increasing of the S.Q. of an audio system...
The devices i created for myself cost peanuts and worked so much that they transform my basic vintage good audio system to a new level ...
Anybody can make them, anybody can create better device at low costs....
Knowing that it is not so much buying better gear, past some point of your purchasing history, that will improve your system, the so called "upgrading process", but the increasing controls of the mechanical electrical, and acoustical dimensions is the most important basic fact in audio life...
Dont upgrade anything before embedding everything rightfully....
This is the basic axiom of audio....
And the ONLY important knowledge for most of us, engineers or not.....