Re: No Sound ????????

i can tell you now the reason why this is happening is because of the way you have your sound setup.

how is your setup all connected?

examples

ps3 >–(hdmi)–> hdtv >–(optical)–> speakers

or

ps3 >–(hdmi)–> hdtv with inbuilt speakers.

or

ps3 >–(hdmi)–> hdtv

      >–(optical)–> speakers

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put simply, TV's don't like re-routing sound. 

if you are re-routing the sound to your amp from your tv through hdmi originating from your ps3, you will get the problem you describe.  this can be fixed by setting your ps3 sound output to hdmi with only 2.1 surround (because that's what the tv thinks the sound source is).

OR the proper way to do it:

Connect your ps3 DIRECTLY to your TV and speakers with hdmi and optical.  a direct connect connection will ensure true surround when your ps3 output is set to optical with 5.1.  make sure you put the correct frequency as well because setting it too high can damage the speakers. check your speaker's manual if you're unsure.

by doing either one of these, im sure you will eliminate the problem.

for additional help, please provide more details about your setup.