Tape duplication

F

Findlay

Member
Apologies if this is the wrong place to post this, or if it has been covered before, but I thought I'd share something I learned a few weeks back about tape duplication. I'm in the middle of digitising my Tascam 244 cassetes and am amazed how good they sound 30+ years on. I wish I could make high quality safety duplicates to work on and will probably copy some of them back onto new cassettes on the 244. But, of course, this will add w&f, distortion, noise, frequency loss etc. A few weeks ago I found out that - amazingly - there is method of direct (mechanical only - no electronics!) copying using what is known as Thermal Magnetic Duplication (TMD). Using this, the new tape is pressed into brief contact with the old tape at about 120 degrees and the original recording is copied perfectly, apparently with no loss or tape damage. Otari made a machine a while back for copying video tape at about 300x normal speed using this:

Otari, Inc.: Product Information: Service Information: Discontinued Products: T-710 Video Duplicator

I am sure I read somewhere of machines made for duplicating cassettes.

The only snag is that you can only use chrome tape - not doped pseudochrome such as SA.

Anyone have any thoughts on this?
 
Findlay said:
I'm not sure what they mean by "Inverted" - is it phase inversion? Wonder what it sounds like!
Click to expand...

They are copying video - the copy would be is a mirror image (what jp called inverted), so they correct that by making a mirror image master first, then duplicating from that.
 
I've just read a little more about this - it seems that only the copy tape needs to be pure chrome - it helps - vital I think - if the master is ferric or pseudo chrome. So looks like it could work with SA and the like if the cassette tape thickness issue isn't a problem. It seems E180 VHS tape thickness is about 18 microns - roughly the same as triple play reel and C60 I think. Just knocked out that you can get perfect copies using a mechanical process!
 
I am not seeing the logic here?
The tapes have to be "played" no matter how they are copied. I would simply copy them into a PC using a decent AI.

There may be other ideas but I would leave and Dolby NR off since the replay machine is unlikely to be perfectly aligned and in any case the tapes are unlikely to have line up tones on them!

Once digitized they are "safe" so long of course that you store the data in multiple locations!

I did a search some time ago for a Dolby B software solution but nothing showed. Maybe now?

Dave.
 
Not sure there is much logic here! I am just intrigued to find out that there is a way of perfectly (losslessly) copying from tape to tape using this TMD process. I would love to have actual tape copies of my best 4-track recordings, not only as an alternative archive but also to work on with new guitar parts and stuff, but copying from one machine to another, or copying back from a digital copy will just introduce extra wow, distortion, noise etc. With TMD there is none of this.

I found a good dolby A and B and dbx emulator at last - U-he Satin.
 
Findlay said:
Not sure there is much logic here! I am just intrigued to find out that there is a way of perfectly (losslessly) copying from tape to tape using this TMD process. I would love to have actual tape copies of my best 4-track recordings, not only as an alternative archive but also to work on with new guitar parts and stuff, but copying from one machine to another, or copying back from a digital copy will just introduce extra wow, distortion, noise etc. With TMD there is none of this.

I found a good dolby A and B and dbx emulator at last - U-he Satin.
Click to expand...

Yes but, if you copy the digital version back to tape using really good tape and a really good machine the result will be virtually the same as the original (dare I say a bit of mild digital noise suppression might even improve things?)

Dave.
 
Interesting. The source is "a high Curie point master tape containing a mirror-image recording of the desired program," meaning that the duplicate tape stock is thermally "scrambled" at a lower temperature than the master tape stock, which presumably is unaffected for many passes. So you couldn't copy one tape to the same kind of tape by this method. Somewhere I read about a similar method of contact printing done by sandwiching a high- and low-coercivity tape together in a magnetic field calibrated to erase one but not the other.

I wonder if there were linearity problems with this method of duplication, or if the heating acted enough like bias. The only signals on VHS/Beta that are not recorded at saturation level are the linear audio tracks, and those usually sounded awful...
 
I've tried copying back the digital version on to my Tascam 244 and the extra w&f and dbx artefacts are just a bit too annoying!
 
pdmillar said:
Interesting. The source is "a high Curie point master tape containing a mirror-image recording of the desired program," meaning that the duplicate tape stock is thermally "scrambled" at a lower temperature than the master tape stock, which presumably is unaffected for many passes. So you couldn't copy one tape to the same kind of tape by this method. Somewhere I read about a similar method of contact printing done by sandwiching a high- and low-coercivity tape together in a magnetic field calibrated to erase one but not the other.

I wonder if there were linearity problems with this method of duplication, or if the heating acted enough like bias. The only signals on VHS/Beta that are not recorded at saturation level are the linear audio tracks, and those usually sounded awful...
Click to expand...


Yes - you could do it with TDK SA masters on to BASF Chrome, for example, as the SA master has a Curie point of about 500 C and the BASF would be about 120 C.

I think the linearity is probably almost perfect from what I've read. I think BASF used it for musicassettes towards the end of their reign and the German engineers wouldn't settle for anything less!
 
You must log in or register to reply here.
Back
Top