[QuadList] Little more fun

Tue Mar 9 17:51:21 CST 2010

 Hi Folks,

The Ampex contact duplicator operated on some very basic magnetic principals, by using a high coercivity mirror image tape held in direct contact with a blank standard tape, a copy was created when the two were placed in a magnetic field, almost like contact printing.

The keys were making a exact mirror image master, hence the AVR-1 mirror kit with the special MK 20 head assy and other stuff.
Also the duplicators clamped the two tapes together in a vacuum while the tapes were ridding over a large rubber faced drum, maybe it was over two inches high by about 10" in diameter and had a vacuum "shoe" that was controlling or clamping the contact area which was probably over 90 degrees of the rotation of the drum and the field was applied here also.

The tapes needed very good hi speed tension
 control, so we used AVR-1 reel motor assemblies. The clamping/drum  assy which was removable like a quad head was the only part the needed rebuilding. 

All I remember is that there was one great engineer in our Sunnyvale/Cupertino plant that could get it done and test it and he never smiled at me when I had another assy. to rebuild.

We had seven systems installed, and another in storage somewhere, with the AVR-1, with the kit installed, ready for one of the eastern oil rich countries, if we would ever get the shipping clearance?

The master tape did not get erased by the transfer field since the coercivity was up at about 1500-2000 oersteds as I remember.

This was called hysteric duplication and you could also do thermal duplication, same principle, but replace the magnetic field with something that would bring the tapes up to the "currie point"
 and then cool them quickly with out melting the backing, which was very difficult. 

CVS, the folks that made the first DTBC in 1973, tried to do this and then had to time base correct to make a good helical master. Once they built the DTBC they forgot about duplication very quickly.

Bill Carpenter

--- On Tue, 3/9/10, georgenann at aol.com <georgenann at aol.com> wrote:

From: georgenann at aol.com <georgenann at aol.com>
Subject: Re: [QuadList] Little more fun
To: quadlist at quadvideotapegroup.com
Date: Tuesday, March 9, 2010, 2:35 PM

Tnx fer info steve.  I wish I was in on that system, sounds interesting.

73,

George

-----Original Message-----

From: Walton, Steve <SWalton at tribune.com>

To: Quad List <quadlist at quadvideotapegroup.com>

Sent: Tue, Mar 9, 2010 5:28 pm

Subject: Re: [QuadList] Little more fun

Hi,

By placing the two tapes together in a magnetic field, some of the magnetic image from the master would be transfered to the blank tape (similar to a print-through).  It left just enough of a magnetic signal on the blank tape to be recoverable by some machines.

Obviously there was a limit to how many copies could be made this way, but I do not know what that limit was.  One would think that every time this process was repeated, the image on the master would diminish slightly.

Steve Walton

From: quadlist-bounces at quadvideotapegroup.com [mailto:quadlist-bounces at quadvideotapegroup.com] On Behalf Of georgenann at aol.com

Sent: Tuesday, March 09, 2010 5:19 PM

To: quadlist at quadvideotapegroup.com

Subject: Re: [QuadList] Little more fun

Hi Steve,

Thanks for the reply about the HS Dubber.  The part I don't quite understand is the RF field, what kind of field was it?  How did it pass the mag info to the blank tape?  Also did it damage the original mirrored master?  I ran into a fellow who worked on one and he told me he had lots of trouble with it, it was a "Bear".

73,

George Keller

-----Original Message-----

From: Walton, Steve <SWalton at tribune.com>

To: Quad List <quadlist at quadvideotapegroup.com>

Sent: Tue, Mar 9, 2010 5:11 pm

Subject: Re: [QuadList] Little more fun

Hi,

It was my understanding at the time (70's) that the "high speed dubs" were first recorded on a special "master" machine (AVR-1?) that was specially manufactured to record a mirror image onto the master tape.  This special machine was identical in all respects to a standard machine, except that it was a mechanical mirror (head rotated backwards, tape ran backwards, I am not sure).  But the net result was that it recorded a tape that was a mirror image of a normal recording.

This mirrored master tape was then copied as stated below by bringing the master and a blank tape into contact and passing them through a magnetic field.

These high speed dubs were easy to spot because they had a very low RF level.  Some machines (VR-2000's) would not play them, but an AVR-1 would usually get them to play without problem.

Steve Walton

From: quadlist-bounces at quadvideotapegroup.com [mailto:quadlist-bounces at quadvideotapegroup.com] On Behalf Of georgenann at aol.com

Sent: Tuesday, March 09, 2010 4:45 PM

To: garyada at ix.netcom.com; quadlist at quadvideotapegroup.com

Subject: Re: [QuadList] Little more fun

Hi Gary,

Actualy, I think if you had the oxide side of the tape on the heads, the heads would be completely slanted in the opposite angle from the recorded tracks.  With the back of the tape on the heads, we didn't get enough signal to make any video at all.

You just rang another bell.  Has anyone run into the Ampex High Speed Dubber?? I only saw one once at EUE in New York, briefly.  I understand an AVR-1 was needed to make a mirror image tape first, then the dubs were made by putting the new mirror tape against the blank and some kind of field was shot thru them and the video was recorded on it.

George Keller

-----Original Message-----

From: Gary Adams <adam7889 at bellsouth.net>

To: 'Quad List' <quadlist at quadvideotapegroup.com>

Sent: Tue, Mar 9, 2010 4:32 pm

Subject: Re: [QuadList] Little more fun

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Because the quad tracks were mostly (not completely) perpendicular to the tape, backwards got some picture upside down and backwards.  You were still reading the oxide side.  This put the control track where the audio heads expected audio so you hear control track.  Capstan would free run without control track.  Some clever people put 240hz tone on the audio track allowing the capstan to be a bit more stable as a joke.  I think newer machines did not like this too much but I’ll bet the AVR1 could play it and probably turn the picture back up  J  (just kidding).   I think on a 1” the tracks would never line up since they were so
 slanted to the tape.  So the heads would read across the track rather than with the track.  

Gary

From: quadlist-bounces at quadvideotapegroup.com [mailto:quadlist-bounces at quadvideotapegroup.com] On Behalf Of georgenann at aol.com

Sent: Tuesday, March 09, 2010 4:04 PM

To: quadlist at quadvideotapegroup.com

Subject: Re: [QuadList] Little more fun

Hi Joe,

This was after FF to the TU reel then puting it on the supply side so it is looking at the back of the tape, we were getting a "Nil heard signal" from the tape.

Now that you mention it I do remember at some time having a tape upside down on a machine, it did come out upsidedown, but bad picture and lock up with a funny tone from the CTL coming out of the audio. BUt this was with the oxide side facing the tape.

Mny Tnx,

George 

-----Original Message-----

From: Joe Owens <jpo at prestodigital.ca>

To: Quad List <quadlist at quadvideotapegroup.com>

Sent: Mon, Mar 8, 2010 5:18 pm

Subject: Re: [QuadList] Little more fun

[Flipping the tape over takeup/supply] On some machines, the video would play upside down and in reverse, but no audio, obviously.

On 6-Mar-10, at 11:49 AM, georgenann at aol.com wrote:

I think this would work on the 1" machines also, but I never tried it.

Joe Owens

Presto!Digital Colourgrade

302-9664 106 Avenue

Edmonton, Alberta T5H0N4

+1 780 421-9980

jpo at prestodigital.ca

= 

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