Is the Bell 6131 a cable or satellite set-top box?
Check the settings for it and see if it is using any compression modes and if possible turn them off. My cable box has something similar and allows you to set the 'audio range' to normal, narrow, wide. Normal seems to be 'leave it alone' while narrow and wide are forms of compression and mess with the audio a bit.
Also check the volume output, fixed or variable. If set to variable, the box's volume control would have to be all the way up and I know with my cable box, any time the power goes out it reverts back to a volume setting of about half. Fixed is a slightly lower output level but at least you never have to be concerned about the position of the box's volume setting.