It was that way with my 6200,3400 and now the same on the gateway.
Running sound thru my receiver via hdmi I have to increase sound by 10 to 15 to equal volume on normal channels.
Its a pain so usually I pick other options to listen to music at home because of the constant volume swing.
This should be I would think an easy thing to rectify.
Any answers would be greatly appreciated, thanx.