The audio came from a fan which is true. I believe it was recorded on a reel to reel tape recorder. I taped DS on such a recorder when it first aired and that is where the audio came from an original broadcast of the show back in 1971. I have many tapes and the recorder and they still play brand new. The credits are fun to hear. The voice overs i mean as you get in year 1 of DS on DVD.
I taped DS with a cassette recorder when the first half of Barnabas storyline aired in Chicago in 1976. I payed 100 bucks for that recorder in 1974. The show then reaired again just the first year of Barnabas and I taped those. The bad thing about the cassette tapes were they would not last.
If you are a mission impossible fan you can see the recorder I used. The exact recorder was used on Mannix and I even taped an episode from the original broadcast of Mannix with my recorder.
There was a talk about why this episode went missing but I cannot remember what people said. I believe it is in this thread. I really like the episode and how Jim presented it to us. Lara speaking and having the sound and pictures she and Jim created a very special episode for me and all fans.