Digitizing Digital Audio Tape: Testing Two Approaches
The Stanford Media Preservation Lab has kicked around the idea of building a dedicated Digital Audio Tape (DAT) "ripping" workstation around a Digital Data Storage (DDS) drive for a few years, but we never pursued it in earnest. We assumed the benefits of using a computer drive to read audio DATs largely centered around extraction time and reporting. Transferring a DAT in a conventional deck is done in real-time, whereas a DDS drive, we were told, would rougly cut the time in half depending on the speed of the drive (Peter Oleksik's retrospective on the Fugazi archive mentioned speeds up to 4x real-time using the DDS method with a Sony SDT-9000 drive and DATXtract). We also liked the idea of accompanying logs identifying where dropouts occurred. Still, we were skeptical whether such a system would be better than one designed around multiple conventional decks. Was there a way to test both methods without investing a bunch of money in late 1990s computer components?
As it turns out, one of the vendors we use for work we cannot handle in our lab had both systems up and running. We proposed sending them a sample of nine DATs, and having them digitized both ways for comparison. DAT digitization can be quite fickle, as playback on one deck does not always match playback on a different deck. We have three different machines from two different manufacturers in the lab, and the same DAT played back in all three can yield different transfers with dropouts potentially in different areas. Even playback on the same deck can produce different results over time.
Sure enough, the vendor transfers followed this pattern. The DDS transfers had much more noticeable and severe dropout that conventional playback concealed. Although we were only working with a small sample set of nine tapes, the DDS transfers were consistently the worst of the bunch when compared using null tests with conventional transfers done by the vendor or us. There was one tape that WaveDAT - the DAT extraction program the vendor used - struggled with, however it played back fine in one of our Sony PCM-R500 machines.
No doubt the DDS method is efficient, but an efficient system that generates poor results is not something we want to put into production. This test confirmed that siimultaneous capture using conventional DAT decks can be as efficient and less error prone. Have you compared these two methods, and if so, what was your experience? Let us know in the comments.