DAT backup strangeness

[yousef]

I wonder if someone might be able to give me some insight into what's going on here...

I'm archiving my old DATs using the following setup: Sony 55ES > [optical] > Iriver h120. I've done eight so far but one is proving to be rather problematic. I've tried transferring it twice and both times the resulting file has lots of little skips - as if a fraction of a second of sound has just disappeared. This doesn't leave a gap, but the next bit of sound comes along early, if you see what I mean. I'm sure there's a far better way to describe this...

The strange thing is that the skips are not in evidence while the tape is playing in, nor are they there when I listen to the tape again afterwards. The six tapes I transfered prior to this one are unaffected and the one I've done since was fine too.

So what could be happening here? I don't think it can be my optical cable as the other tapes aren't affected and it seems unlikely to be the Iriver's hard drive.

Is there a reason why the same recording going through the DAT player's ADC would emerge fine through my hifi but the digital stream to another device would contain errors?

Any ideas would be much appreciated.

[F.O.Bean]

bad or misaligned or dirty heads?

[yousef]

bad or misaligned or dirty heads?

This had crossed my mind but I ran a cleaning tape through before starting to play through the tapes and it does seem to be this particular tape that is solely affected. DATs taped on the same machine around the same time, as well as before and since, seem to play back without problem.

Also, would dirty or misaligned heads allow the analogue out signal to be unaffected while the digital output was skipping? I may not have made it clear before, but I was listening as I transfered this tape and didn't notice any of the blips that subsequently became apparent.

The only thing I have been able to think of is that the tape is past its best and that the error correction on the 55ES is correcting things before I hear them through the hifi but that the optical output is the raw, uncorrected stream.

I have no idea if this is possible but it's the only explanation that I can find thus far. Aside from a dodgy optical cable that has conspired to malfunction only when this particular tape is playing...

Thanks for your input - I'll try another batch of tapes this week and see if any others are affected.

[F.O.Bean]

I had lots of DAT errors when transferring to HD's. I just chalked it up to misaligned heads and moved to the next one!

[Since85]

hi,

If the tape sounds fine while the DAT is playing, I would try one (or a combination) of these:

1. Look at sample rates. For example, if a tape is recorded at 48, and you transfer to 44.1 on the fly, the sample rate conversion may be causing the skips. Import the data at the same sample rate that the DAT is playing (e.g. both 44.1 or 48). Make sure the sample rate of the iRiver matches what the DAT deck (Sony) is outputting. If needed, change sample rate in post.

2. Is the optical (Toslink) connection working fine with other devices (both the Sony and Iriver)? A dirty toslink cable/port can cause bits to drop, and skip. Test the connection with other devices if possible.

3. Just to rule out the head issue, see if the Sony deck has a mode to show error counts, or try playing the DAT on a deck that does output error counts. If the error counts stay low, you will be able to eliminate that concern.

Hope this helps!

[yousef]

Thanks for the advice - a couple of things to be thinking about there, I think. I think the Sony deck does show error counts, I'll have to find the manual.

I'm definitely going to run a another glut of tapes through and see how often this happens. And I'll dig my D8 out and see if it plays back any better through that. But I know that was worse for wear the last time I used it...

I had lots of DAT errors when transferring to HD's. I just chalked it up to misaligned heads and moved to the next one!

I wish I could do that but I'm determined to get clean transfers of all of them. I stuck with the damn format for much longer than any sensible person should have so I reckon those little tapes owe me...

[sunjan]

hi,

If the tape sounds fine while the DAT is playing, I would try one (or a combination) of these:

1. Look at sample rates. For example, if a tape is recorded at 48, and you transfer to 44.1 on the fly, the sample rate conversion may be causing the skips. Import the data at the same sample rate that the DAT is playing (e.g. both 44.1 or 48). Make sure the sample rate of the iRiver matches what the DAT deck (Sony) is outputting. If needed, change sample rate in post.

2. Is the optical (Toslink) connection working fine with other devices (both the Sony and Iriver)? A dirty toslink cable/port can cause bits to drop, and skip. Test the connection with other devices if possible.

3. Just to rule out the head issue, see if the Sony deck has a mode to show error counts, or try playing the DAT on a deck that does output error counts. If the error counts stay low, you will be able to eliminate that concern.

Hope this helps!

All good advice! I'd start with checking that the output really is 44.1kHz, before moving on with the resto of the troubleshooting. For the H120, also make sure to feed the signal into the optical jack before powering up the H120. Otherwise strange things can occur with the sample rate...

[yousef]

All good advice! I'd start with checking that the output really is 44.1kHz, before moving on with the resto of the troubleshooting. For the H120, also make sure to feed the signal into the optical jack before powering up the H120. Otherwise strange things can occur with the sample rate...

Indeed. One thing I've fallen foul of is if I have two 44.1kHz recordings on one tape with a small unrecorded segment in between - the player snaps into 48kHz mode for the gap and the Iriver follows suit but doesn't switch back to 44.1kHz when the next recording begins (even though the player makes the correct switch back to 44.1).

[nic]

while I cannot remember the specifics, a couple of years ago there was a bad batch of DAT/DDS tapes made (I know Sony was one of the resellers).
it could be that this "problem" tape could be from that batch...

[Jammin72]

It's not tape or error oriented if it's playing back on the machine with no audible skips or gaps.

Stick with the sample rate theory!!

ID markers between machines can also get translated kind of funny.

[esteyes]

just as an FYI, analogue from the dat deck is passing thru a D>A converter. part of that converter's function is to perform error correction on the digital stream. so it is possible that the reading of the tape is not perfect (ie missing bits), but the D>A process is masking the errors by correcting the missing data via interpolation. that would explain the analogue audio from the deck sounding good but since the Iriver is getting the corrupt data stream w/o error correction, its audio output could be hosed.

now this is assuming that the sample rate issue is a non-issue...

if you know someone with and R500 (Sony), hit them up for a transfer. those decks have awesome abilities to read tired tapes - i own two, as well as a multitude of other brand dat decks and the sonys do the best. plus, keep trying that tape in other brand/model decks. a dat deck is a mini beta deck - that means alignments are unique - you might just find one that will play that tape. (i have a whole lotta pcm-beta dead. i actually have 5 beta decks each with a slightly different alignment setting so that i can get them old tapes to play back w/ a minimum of drops)

neil

[yousef]

Thanks for that, Neil - I had wondered whether error correction on the analogue output might be masking the problem.

I'm going to try another batch of DATs this weekend, including re-trying this problem tape, and then see if using the D8 that the recording was made on makes any difference. And then I'll reassess.

+Ts to everyone for all the help and advice - it's much appreciated and really does take the sting out of what could be a really frustrating problem...

[morst]

Is there a reason why the same recording going through the DAT player's ADC would emerge fine through my hifi but the digital stream to another device would contain errors?

Yes. You have to sync the recording device to the digital clock of the source. If you attempt to use the internal clock of the target machine without locking onto the clock signal from the master source, you will get skips like you are describing. In order to transfer DAT's digitally into my Protools system, I have to set the computer's input to DIGITAL and the sync to EXTERNAL. Good luck with this!

PS if you have to transfer things via analog, you'll probably be able to see the difference (low level noise) in the wave editor software but not be able to hear it. 

[yousef]

If you attempt to use the internal clock of the target machine without locking onto the clock signal from the master source, you will get skips like you are describing. In order to transfer DAT's digitally into my Protools system, I have to set the computer's input to DIGITAL and the sync to EXTERNAL. Good luck with this!

Thanks for that, but I wonder whether my rather basic setup has the scope for this. I think the Iriver options go as far as enabling the optical input and then plugging something into it...

PS if you have to transfer things via analog, you'll probably be able to see the difference (low level noise) in the wave editor software but not be able to hear it.

This is one of the more annoying things about this - I'm quite satisfied with the original transfers I made of these tapes (even though it was through the resampling digi-in on my Soundblaster soundcard), I just wanted to get definitive bit-perfect transfers for archival purposes, rather than anticipating a huge improvement in sound quality. But it never quite goes to plan does it?

[morst]

I just wanted to get definitive bit-perfect transfers for archival purposes, rather than anticipating a huge improvement in sound quality. But it never quite goes to plan does it?

QFT. I had to do analog transfers for a while when my 7-pin "oade cable" broke. I can't hear a difference. In order to keep the "bit perfect" archive going, I simply save the master tapes and don't play them back too many times!!