Have you tried this step by step guide :: spam link removed?
It lets you convert DTS to FLAC as well as keep the channel of the source file like 5.1 DTS to 5.1 FLAC, the same to DTS to WAV.
It also help you convert 5.1 FLAC to DTS/5.1 DTS, 7.1 FLAC to DTS/5.1 DTS while keep high output quality.
Hope it will help you more or less.