Help on RPTV Sound

[Gregavi]

I have a Hitachi 61SWX10B about 3 1/2 years old. Recently the sound has been crackling and gets worse until it goes out completely . When I first turn on the set, it's okay for a few seconds and then the crackling to nothing sequence starts. So I turn the sound all the way down and listen through my Preamp/Amp setup. No problem there. I had to replace the convergence chips last year and it was fairly simple once I knew what to look for. Is there a "Sound card " or Sound Chip" that is likely going? If so, is this fairly simple to replace as the convergence chips where? Any help or advice is appreciated.