Topic: DAT playback help

[alzeppelin]

I've been tranferring some old DATs and ran into an issue with couple of them that I have never encountered before.

When I play back the DAT on my Sony deck everything sounds find on the analog outputs but when I attempt to use the digital coax out the left channel continually peaks out, even when it is on a dead portion of the tape.  This problem only occurs on this specific DAT while all of the rest of them play properly when using the digital output.

My hunch is that this has something to do with SCMS protection but I don't know much about it so I was hoping someone on the board could fill me in.

Has anyone ran into this problem before?

[ScottT]

Bad coax cable?  Dirty connections?

[alzeppelin]

That was my first guess but every other dat I play is totally fine with no issues whatsoever using the same digital coax.

[darby]

That was my first guess but every other dat I play is totally fine with no issues whatsoever using the same digital coax.

Alex, if you can't figure it out send me the DAT(s)
and I'll try to transfer them with my Sony R500

[H₂O]

Tape or deck could be slightly out of alignment - creating subtile errors on one of the channels that are intereperted differently by your downstream digital device.
 
Tape could have been recorded with a deck that is slightly out of alignement to your deck.

[dgale]

What's wierd is that is sounds from the description like it monitors fine?  Does it sound fine on headphones from the headphone out of the deck (i.e. listening to it on phones from the DAT deck and not from the phone out of wherever you are sending the digital signal) but the digital signal is funky?  If the deck was out of alignment or more likely, the DAT in question was recorded on a deck that was out of alignment (and hence the tape will only play back correctly on the orignal mastering deck, assuming it's alignment hasn't since been fixed, or else on a different DAT deck that is more forgiving), then it should exhibit the problems via all outputs and not just the digital out.  I've dealt with a fair number of tapes in the past that give playback issues but I've never encountered a situation where the digital out signal is funky yet the analog and/or headphone out signals are not. 

[DSatz]

If I recall correctly, SCMS prevents the player from emitting any digital bitstream if the flag bits in the recording have marked it as restricted.

You may be confusing SCMS with the various copy protection schemes that have been used on commercial videotapes and DVDs, which emit a video signal that can be watched on a TV set--but various shenanigans in the vertical interval make it difficult or unprofitable to copy the same signal.

Unfortunately I don't know what's causing the problem you're describing, but I would try playing back the tape on another DAT deck. Despite the elaborate auto-servo-alignment system that's part of the DAT specification, I remember from the early days of this medium that if a tape was recorded on a Panasonic, you had to play it on a Panasonic and not a Sony, and vice versa.

Of course all DAT recordings from back then have deteriorated by now to the point of being marginally playable at best no matter what deck you used--but I would only expect that to intensify the problem of tape incompatibility and the need to play back certain tapes on certain machines.

Again, all this need for concern is completely contrary to the design of the medium, but it's the way things worked out in practice nonetheless. "The best-laid plans of mice and men ..."

--best regards

P.S.: In my experience, full-size DAT decks sometimes play tapes back more reliably than ultra-miniature, portable recorders; many of the portables have half-sized head drums and force the tape to bend around a very narrow radius, while the tape-to-head contact on the larger units seems to be better.

[alzeppelin]

Yes, the signal out of the analog outs including the headphones sound perfectly fine.  The more I think about it, it may have to do with the original deck it was recorded on being out of alignment.  Like I said before all of the other DATs I have played in it sound perfectly fine since them were originally recorded on different decks.  All of the ones I am having the issues with originated from the same deck.

It is still weird how it is just the digital signal that is having the problems while the rest are fine.

What's wierd is that is sounds from the description like it monitors fine?  Does it sound fine on headphones from the headphone out of the deck (i.e. listening to it on phones from the DAT deck and not from the phone out of wherever you are sending the digital signal) but the digital signal is funky?  If the deck was out of alignment or more likely, the DAT in question was recorded on a deck that was out of alignment (and hence the tape will only play back correctly on the orignal mastering deck, assuming it's alignment hasn't since been fixed, or else on a different DAT deck that is more forgiving), then it should exhibit the problems via all outputs and not just the digital out.  I've dealt with a fair number of tapes in the past that give playback issues but I've never encountered a situation where the digital out signal is funky yet the analog and/or headphone out signals are not.

[dgale]

If the tape was recorded on a deck that was out of alignment and is now being played back on a deck that is in alignment (or has a different alignment) then I'd expect it to have issues both on the analog and digital outs - I can't really see how this problem would only occur on the digital out.  I mastered a few shows on a deck several years back that was out of alignment and when played back on a different deck, it had lots of digital noise that was the same regardless of digital or analog out. 

As a side note, I was foolish enough to send the deck off to be repaired before I cloned the masters and when the deck returned, it was fixed perfectly but I was never able to get those masters to play withouth flaws.  I was able to have better luck on some of my decks than others, so it's always worthwhile advice with DAT playback issues to try a variety of decks.  In some cases I was able to get most of a tape to transfer fine via one deck and then get another deck to play the portion that had playback problems with deck #1, while deck#2 wouldn't play most of the rest of the tape okay.  Trial and error and I eventually got all of the pieces to play okay via one deck or another and then splice them all together with SoundForge.

[darby]

this is why I don't miss using tape

[dgale]

this is why I don't miss using tape

I agree but there have been times I've recorded on my laptop and had it hiccup in a few places to create flaws in the master WAV file...and I was glad I had plugged a DAT deck into the 16bit output of my AD2K as a back-up...I was able to splice in to replace the corrupted sections and all was good.  Of course an even better solution would be to have a secondary 24bit recorder as a back-up.  Then again, these problems only happened when I recorded on a PC laptop...now that I have a Mac, they of course will be a problem of the past 

[alzeppelin]

I'm making the jump to harddisc recording but unfortunately I still have a decade of DAT masters that need to be backed up.   

These tapes are not getting any younger too so I'm at a race against time before they could possibly start deteriorating.