Decades, and decades ago, I performed some listening tests and the results surprised me. Wanted to see if there was a difference in ics back then, as was advertised. Kind of a different test, but somewhat simple to implement.
I made two pair of ics, same copper wire, same insulation, same capacitance, inductance, and resistance. Output impedances (Z) and input input Z of amp were approximately 2k and 100k ohms respectably. Ic capacitance ~40pf.
One pair of ics had plugs, one end plugged into my source jacks and the other end into the 10A line preamplifier jacks.
The other pair of ics was bare wire ends soldered to the source jacks (inside chassis), and soldered to a different inputs jacks on the 10A (inside).
The selector switch was used to select between the two different ics.
The sound was different, quite different between the two different ic pairs.
The entire system was common to both pairs of ics except the ic connection techniques.
I then compared two different type plugs with common termination techniques, different sound, so plugs make a difference.
I then compared two different termination techniques on same type plugs, so termination techniques also make a sonic difference.
Lastly, a listening test was devised/setup to check ics for accuracy in absolute terms. (The small variable is the jacks that the plugs mate to.)
Ics, make a sonic difference alright.
cheers
steve