Dolby 5.1

[Rob van der Does]

AV boxes cannot decode AAC.

Except those that can

There are indeed amps that are capable of decoding AAC. But because most AC3-capable amps can't, there is a dedicated downmix for AAC available on many boxes.

And as has been suggested before: you can turn the volume of the box a bit lower, so all PCM sound will be less loud.

[adm]

And as has been suggested before: you can turn the volume of the box a bit lower, so all PCM sound will be less loud.

This may work with AV amp that decodes AAC but not with any connection reliant on the downmix and output as PCM. The MB volume control controls the downmix volume for both surround sound and non-surround sound broadcasts (HDMI, SPDIF and Analogue RCA) so there will always be a perceived 2:1 difference in loudness when the broadcaster changes, which usually occurs during the continuity announcements at the end of programs or for adverts.

Set the MB volume to, say, half scale for a surround sound encoded broadcast and set the AV amp for an optimum sound level and it will change to around twice that perceived level when the broadcast program ends.

Even if you take the AV amp out of the equation by feeding the HDMI directly into a non-surround sound capable TV and using the TV speakers or using the RCA analogue outputs to an 'ordinary' stereo amplifier there is a perceived 2:1 sound level difference.

Sound balancing for UK HD terrestrial TV is probably impossible with the MB unless connected to a AAC capable AV amp that bypasses the MB downmix.