Do not use this unit within 22 cm (9 inches) of persons ... Do not use an 8 cm (3”) to 12 cm (5”) adapter ... Steven M. Schweda, Christian Spieler, Cosmin Truta ...
https://asia-latinamerica-mea.yamaha.com/files/download/other_assets/2/332022/BD-A1040_om_AL.pdf