Unfortunately that's not possible. I don't turn it off any more. I looked at the standby power consumption and it's almost zero.

No. Unfortunately, it is not possible to switch off the startup sound. This can only be avoided if it is connected via a jack. But that's not the point if I want a device without a lot of cables. I also tested the connection via BT for several hours on the PC with video. There are minimal delays and the picture is not 100% synchronised with the sound. I'm sure not everyone notices this. For me, the Z407 is therefore not usable. Goes straight back. Unfortunately very disappointing. I'd prefer the Z625 with optical input. Better sound, better workmanship and no unnecessary music when switching off or on.

This start sound at full volume is absolutely annoying. You should not buy this product.

It also bothered me enormously, especially when my wife wanted to go to sleep... I managed it, but I don't know how :-( Maybe it's because I connected the Z407 to the PC via a 3.5 mm jack instead of via Bluetooth, and set it that way via the PC settings? In any case, it remains mute now.

It is not possible to turn off the startup sound.

I can't answer that. I don't use it myself. It was bought as a gift.