Problems with sound from XBMC -> ATV 2

Hi
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My setup is!!!
I have a ATV2 running 5.0.2 (4250) and its been jailbreak with Seas0nPass. after that i have installed XBMC

My ATV2 is connected like this

Sound = From ATV2 i use optical cable to my sony reciever ( i have no HDMI ports in my reciever)
Picture/movie = From my ATV2 i use HDMI to my Panasonic Plasma

The movies is .mkv and is ripped with all audio and subtitles and i use a Synology NAS to streem the movies to my ATV2

Sony STR-DB930 (reciever) 5.1 with DTS and Dolby digital

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When i streem movies to my ATV2 I have a problem with all the movies that only have AC3 5.1 and not DTS there is no sound... if i choose a movie with DTS the sound is perfect i have tested the same movies with AC3 5.1 and with DTS playing on my playstation 3 and here there is no problem with the sound. so the problem have to be in XBMC.

the settings in XBMC is.

Audio output optical/coax
speaker config. 5.1
enabled - Dolby digital (AC3) capable reciever
enabled - DTS Capable reciever


i have tryed disable above and then get downgraded sound in 2 channel

does anyone have a solution or do i have to buy a new reciever with HDMI so so i can streen directly to reciever and them to plasma.

thanks in advanced