Hello, I have a 26 inch Westinghouse tv with tinny sound. I bought a pair of Logitech computer speakers but when I plug them into the headphone jack of the tv, nothing changes. I couldn't find anywhere on the tv settings to change the audio source. Do I need a different cable? I saw a video where the speakers were hooked up with an RCA cable that had a male adapter for the headphone jack, but I can't find one of those anywhere to purchase. What am I doing wrong? Thanks,