Eco mode, even when engaged is only active below a certain volume level. IIRC it’s like -40. Once you get above that volume IE:-30 eco basically isn’t in use. So if you’re listen quietly, it’ll be active, but I don’t believe anyone can hear a difference. @PENG has covered this so I’m going to summon him to fill in the gaps. I use eco with my Marantz, and a Yamaha amp on my mains. Can’t tell a difference in actual use but my MV is at -30 as the default when powering up. Maybe that’s why... but due to the design, I doubt you can tell.