I know version 1.29 and 1.46 are the two current firmware versions dts is sending out. I heard 1.29 is for decks with the older (non-Teac) drives and card and 1.46 is for the new drives. However, I've heard of people using 1.46 in older units, even original 2 drawer decks, so only Karen will be able to answer that one.

Other versions caused lots of odd problems, like a split second of silence between reel changes and such. I wish I knew more about this to answer this question, but then again I also wish I knew what the different revisions did period.

All discs I've tested are fully backwards compatible though. If you have one of the current two firmware versions, you can play anything all the way back to Jurassic Park without problems.

Also, all 6-track discs are fully compatible with current units. Even JURASSIC PARK discs.

BUT, stereo discs are no longer available and haven't been for many years. If you have an old print with "stero" discs and have a DTS-6 with the 2-track digital out still connected into a CP, you can get "stereo". But, why? Would't you rather have 6-track? We did very few film in 2-track digital (aka "stereo").