When I first started upgrading, I could hear the difference. However, I couldn't always tell if the upgrade was an improvement, just different. Eventually I learned.
I hit diminishing returns when I couldn't hear a difference after an upgrade. But there was still a cumulative effect from multiple upgrades -- like I couldn't hear differences each time when upgrading amp, preamp, and cables, but after all three upgrades, I could hear the sound was better.
So I kept upgrading until I got to a level where my ears/brain had stopped learning and I really couldn't tell any more.
I hit diminishing returns when I couldn't hear a difference after an upgrade. But there was still a cumulative effect from multiple upgrades -- like I couldn't hear differences each time when upgrading amp, preamp, and cables, but after all three upgrades, I could hear the sound was better.
So I kept upgrading until I got to a level where my ears/brain had stopped learning and I really couldn't tell any more.