I have a 42LB5600-UZ which only has audio optical out. I have an old stereo that only accepts RCA inputs so I bought a converter that translates optical audio to RCA. It works perfectly for my Chromecast audio, and Xbox One, but when I have the audio coming from OTA TV signals, it's just continually crackling from the speakers. I had read online that these converters don't handle Dolby Digital signals and it looks like that's what mode it's set in by default. Under the Audio menu I can disable the internal speakers but I have no option to change the type of audio (Bitstream to PCM) like with other TVs. I'm willing to bet that it can be set in the service menu but I can't even get into that. I've tried holding the menu on the remote like other TVs but the menu never disappears; I've tried holding the OK button; I've tried turning off the TV and turning it on while holding the Menu button. Nothing has worked. I checked out a slightly newer model LG TV at work and that TV has the ability to change audio output types. It's also a newer firmware. Firmware version is V03.00.13.00. I can't find newer firmware anywhere online, including LG's site. I've found the internal service manual which doesn't list how to access it, nor does the consumer manual. Any ideas?