First i dont need to use the loudness button of my Sansui because of my acoustic control of gear and room...In fact even if they can be useful i forget to use them because of the very quality of my system/room at all level...
Second i dont like generalization that are evidently wrong: loudness is useful at VERY LOW volume listening for some people in particular in MOST ordinary non dedicated room... I dont use them but i tested them...The usefulness of this button is dependant of the very low level of decibel used and asked for ...
Many people anyway listen music at high level then they dont neeed this button before reaching premature deafness .... 😁😊
By the way , I am pretty sure that i had learn already how to listen if i was able to tune my own room even creating a " mechanical equalizer" myself in the last 2 years of my listening experiments in acoustic...
And also it is impossible to tune a room by listening experiment and using the loudness button at the same time, then i never use it during the tuning process...
But this fact dont make the loudness button a device for acoustically unrefined ears only.... it is useful at very low level listening... This is an EVIDENT fact....
Then buy a mirror before judging device or other people around your own navel ...
The sansui au7700 is a amp 1975 i had the au417 that was mine first amp. That was 1977 with AR speakers and a dual turntable. I never used the loudness button.
Sorry but if you like loudness you dont know how to listen