Hi, and Welcome to BeoWorld!
Sorry your Avant has gone all quiet on you - and to be honest although there is a mute function on the Beo4 (where the volume 'rocker' button is - push it dead in the centre) i would have though turning the TV off and on again would cancel this.
Sounds like a visit from the engineer, but i'm sure someone will get to the root of the problem on here for you if it's 'user error'!
What was the last thing you did with the Avant? Used a camcorder, Game Station, or did you have a play in the menus - or nothing!
Lee
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