This is really puzzling me. I'm almost finished with my DAT transfers, from a total of 650 down to the last 60. I was using my DA-P1 to transfer until it died last year. For the last 7 months or so I've been using: TCD-D8 >S/PDIF >DR-100mkII.
(Thanks to Randy Vogel for the loan of the digital cable.)
Out of five DAT machines, the D8 is the only one that still works, so I can't really check some of these problem tapes on another machine.
The problem is, I'm experiencing errors in the last part of the tape, usually starting about 90 to 100 minutes into the tape. Some times it's just a few and other times it's many. I always unpack the tape by doing a FF/RW before the transfer. Most of my DATs have been stored tail out. I've hardly ever had errors in the first part of the tape. If they are present it is ALWAYS toward the end. Why is this? I seem to remember that the Sonys seemed to be more forgiving than the Tascams as far as errors. If I had a tape that errored on the DA-30 usually the D7 or D8 would play it. I don't remember this happening before. Is it because of age? Some of the DATs that I have transferred that are almost 20 years old play fine, and some that I copied from a friend's collection in 2001 have problems, but Only at the end of the recording. Yeah, that's still a long time ago...
It's not specific to one particular brand, though it seems that TDK DDS tapes are the worst.
My DATs have been stored in the wooden drawers of my library card catalog cabinet. I live in California, near the coast, away from high temperatures and humidity. The DATs were never played except to copy to another DAT for a trade or to be transferred. (I never wanted to just 'play' tapes because of worries of added wear and tear on the machines.)
I found errors all through a Zero DAT last week, but I figured that was because of poor head alignment on the original record deck. It's a shame, because that one was a first clone of a AKG 414 >HHb PDR 1000 master and I've never seen that source before. (Ventura Theater 1998). I don't remember the taper's name, but I got it in trade through DAT Heads in late '98 or '99.
Fortunately, I have transferred my masters already. These are the last of my trade DATs, though some sources don't seem to be in circulation.