The ps3 should have the regular red,white and yellow rca cables right?
You can just use the red and white for sound. If you need to use a 3 pole mini jack, there are sound cables that have RCA connectors with a mini jack at the other end. You won't get surround sound but at least there's sound output.

Creative used to sell external sound cards (Extigy,DDTS-100) that can decode surround sound from digital inputs like coaxial or optical cable without a pc. Unfortunately those were phased out with no replacement models.

Are there any internal sound card that can do digital input from a coaxial or optical source and can decode the surround sound signal? If there is, you could use your pc to do the surround sound decoding. Downside is that the pc has to be on to do so.

The only other option left would be to get an AV receiver.

Without any surround decoder, there's no way to get surround sound out from the optical input. Hardware/software is required to convert the incoming digital signals to analog signals for the front,rear and center speakers.

Simple answer is you can't get surround sound from the ps3 with your current setup. You need an additional piece hardware to decode the digital signal to get the surround sound. There's no simple adapter that can do this for you.

The ps3 is just there to provide the surround signal, not decode it for you.

The answer that you want is already in my previous post. Get an external sound card that can decode surround without a pc or get a internal soundcard that can accept and decode surround sound.

If you can't get either of the these, go buy a home theater system with surround sound capabilities.

No, I mean use a pc with a sound card that can accept the optical input and decode the surround sound signal. Plug your speakers directly to the pc to get the surround sound.