I don't know if this will help but worth a try. I own a PS3 and connecting with only HDMI cable to TV and the TV to output with normal 3.5 mm Jack to my Altec Lansing or nice 2.1 system PC speakers. It would be good to know that I got as well a Samsung LA40A550P1 series 5 model. So, any model before and after even LED we should all share the same issues or solutions.
The problem: Samsung or technicians and other console / pc manufacturers know this, there's a compatibility issue at certain times when we are connecting via the HDMI or SVGA cable Jack. I've not tried it with optical cable yet but bet it's got the same characteristics.
Now, i've tested with third party 1.3 HDMI cable (claims to give full HD picture deliverability), mid quality 1.3 Microsoft HDMI cable & Sonys Category (1.3a or higher) 2.0 high speed HDMI cable which is supposedly the better HDMI if you want something below $60. There's monster cables and such but I was just tired of testing.
Solution: with Samsung, I notice that Port 1 & 2 of HDMI behaves very objectively, if it doesn't like your cable (HDMI) then it totally won't work. Plug it into your HDMI port 3 and you'll see whether there's no sound, intermittent sound or delayed sounds with slight chirpy glitches like there's not enough power to the sound signal.
Hence, I'd say use port 1 or 2 and get a high speed cable, splurge a little more than $40 or $50 you'll see the difference. It's not so much on the brand but the ability of the cable to deliver the data at a high speed. Allowing the signals of both sound and graphic to go through. I'm quite a prudent spender so I don't spend more than my budget, so you'll get what I mean when I say "buy this" it just means that... And more importantly it should work.
All in all, if it works for me, it'll work for you and your Samsung.
"now, if only Samsung spent a little more about focusing on quality control and testing on their TVs before they push them out to the market..."
PS: As for the SVGA cables, my advice: try not to get those black square headed cheaper ones. Go for true SVGA blue headed (smaller headed connectors) that you normally see people in Dell using a connection between the CPU and their PC LCD monitors. Yes they cost more that's why it'll work for us if we want PC to Samsung LCD TVs :)
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