I will post a tutorial now on how to build you own cable and what you will need.
1) HTC Audio 2.5mm/USB Splitter Cable can be found here
http://accessoryone.com/htc-utstarco...s-pr-5594.html
these also came with the 6800 and 6900.
2) A standard RCA cable cut in half
Steps to Build your cable
1) Start off by striping back the wires from RCA cable and from the 2.5mm side of the adapter cut off the end you wont need it. DO not cut off the metal shielding from the cable just peel it back.
2) Remove the no.4 pin from the ext-usb end. I will provide a pic to show which pin is no4. This will allow the phone to see the adapter as a video adapter instead of a headset. I used a thumb tack to lift the pin and a small set of tweezers to remove it.
3) Now the fun part. The wires on the 2.5mm adpater are RED,GREEN,BLACK,BLUE,WHITE,YELLOW - You will not need the yellow wire so cut it off.
4) Heres how to build the cable connect.
WHITE - Positive for VIDEO
BLUE - Negative for VIDEO
BLACK - Positive AUDIO Left
GREEN - Positive AUDIO Right
RED - Connect both Negatives for audio to this wire then ground this to the Shielding ( I noticed a little ground noise in the audio if i didnt connect the audio ground to the shielding )
Pics are Below i know it sounds confusing but it really isnt.