My hitachi tv has an option to adjust the default sound level for a particular channel - you might want to see if your tv has the same option, if the levels are consistent it ought to solve your problem.

With cable tv like I have, the problem is poor quality control back at the company's main distribution outlet. There should be a 'master control' room that checks the levels of everything going out. I suspect it's something about your converter box, since it's a new issue.

Take a look at the manual or the internal menus if it has them, or the manufacturer's website and see if they offer any solutions, otherwise.

It was 30.00.

When I wrote to our local station's chief engineer he said the network insisted that output levels be at a certain point while other networks required other levels. It's
so bad that I sometimes avoid stations if I find anything
even remotely interesting on an alternate channel. I
am using OTA signal not cable. But the network still is the one who sets the level to cable and
it's probably in the contract what audio levels must be maintained to the public if they
are to be allowed to broadcast.