Using 3.5mm to RCA cable with HDMI cable but no sound

Im using an HDMI cable with my macbook pro (Moshi Display port to HDMI) and have been able to get video on my tv but no audio. So i went and purchased a 3.5mm to RCA cable to plug into the headphone jack of my macbook and then i plugged the red and white jacks on the other end into the red and white audio jacks that are grouped with my HDMI inputs on the tv. But still no sound coming from my tv. Any advice on how to get sound?? Thanks!

Not without knowing what Mac you have along with the make and model # of the TV.

If your Mac is one that passes audio thru the mdp, and you bought the correct adapter, then you can head into Sound preferences and select your TV.

I have a 13.3" uniboy macbook pro (bought it in December 2010). the tv is a Sony Wega 50" its like 5 or 6 years old. almost positive its the KDF-50E200. sorry for the lack of info. help help would be GREAT!

It was brand new current model then or what is the CPU speed?

it was brand new when i bought it in december. 2.4Ghz intel Core 2 duo processor. Has Mas OSX 10.6.6
Thanks!

Then:

bobtomay said:

If your Mac is one that passes audio thru the mdp, and you bought the correct adapter, then you can head into Sound preferences and select your TV.

Click to expand...

as the output.

Thank you!! works great now! really appreciate the help.