[QuadList] Responding to: Excellent Exchange - Non-Contact Extraction of the Program from Quad Tape - Ampex non-moving head

[allanmc-avtech at comcast.net]

Quad.List, 



I think it is evident this group has a vast amount of knowledge in regards to the quads and the challenges of getting the head to tape contact right while maintaining correct tip penetration.    To the several good comments made already let me reply with my thanks and appreciation: 

- I acknowledge that good tape which has been well stored and handled correctly can still be played in the conventional manner.   That's an established fact.  However, my purview at the Library encountered a higher proportion of problematic tapes which came to reside there after being stored and handled improperly prior to being received and deposited at the LoC .   I'm glad to hear that is not the case for the majority of the tapes the group is encountering.  

- About the Ampex High Speed Duplicator.    At Byron's Motion Pictures in Washington, DC, we had one.   In my experience running it I admit to being fascinated by the manner in which the magnetic signal was transferred from the Master tape to the Slave tapes as it passed through the Transfer chambers.  Would love to know more about the manner in which that occurred especially since that section "Theory of Operation" in the Ampex manual was blank!  But, let me reflect upon the process to point out some interesting issues for further consideration.   We had to make a Mirror Master on a specially equipped AVR-1 that laid down a reversed quad strip and also recorded the CT on the opposite from normal side of the tape.   I "believe" but do not know for sure that the Mirror Master tape was recorded at a higher saturation level in hopes of overcoming signal lose in the transfer exchange process when the tapes were running oxide side to oxide side through the transfer chambers.  Obviously, the audio head stack also had to be reversed and its tracks recorded on the opposite side from normal.  All this reversing from normal orientation was necessary to get the correct transfer mirrored image into right orientation on the slave copies.  The High Speed transfer process worked well assuming that we ran precise new tape for all the slave copies.   Problems were encountered when our leaders assumed we could use re-cylced bicycle tapes for the slave copies.   Edge damage and physical imperfections in those returned tapes caused havoc on the Mirror Master tape when they ran at high speed (was it 150 ips or something even higher speed???).  Any way, if the Mirror Master tape was correctly made and if the Slave tapes were new and good quality... the result was a playable dub copy... although the RF tape off the Slave tapes was always a good bit lower than what I as an operator would have liked to have seen.  

Lessons learned the hard way !   We learned "by negative experience" not to check the slave tape copies on another AVR1 machine before shipping to the customers.   As  you know, the AVR1 would play a tape without requiring a CT signal!   And one of our mastering runs had been recorded from Mirror Master CT Record Head that was defective or clogged.   So no CT was transferred onto the Slave copies.   Therefore, all the stations down line received tapes that would not play back on NON-AVR VTRs !   Boss was not happy about that.  

- I hope to learn more from this discussion about heads and tip penetration.   But, don't we limit ourselves by assuming that the non-contact extraction method must duplicate that same method?   What if a newer technology could scan the surface of the quad tape, reproduce its magnetic signature, and then apply algorithms to simulate the distortions and errors imposed by the Time-Base system and the negative head to tape clearance problems originally imposed by stretching the recorded tape over a moving HOT record tip at high speed.    Hey guys!  Forgive the simplicity of my question.  I'm just hoping to come to this problem of recovering our problematic tapes in an efficient manner.   

- Last comment for now.   When our job is to focus on one special quad tape I think most of us can still invest sufficient time and brains to make it play as long as the oxide stays on the tape.   But, the challenge that large institutions like the Library of Congress in the NAVCC faces is that they have such a huge collection and the budge for an expert transfer staff is limited.  The labor cost associated with playing and mastering hundreds (or dare I say thousands?) of quad tapes becomes simply staggering, especially in these days of shrinking federal budget allocations.   So, I'm now realizing that I failed to originally state my question clearly.   Not only is there an interest to play back problematic tapes in large numbers at the NAVCC , but it needs to be done economically.   And economy becomes a vital part of the formula when they will look at a very limited budget which may only enable a small number of "gray haired old guys with expert eyes" that are necessary to re-master their valuable, but sizable, collection of quad tapes.   In my opinion, my friends who remain at NAVCC might be attracted to a new method of recovering the programs from those tapes in a dependable and economically way that is not based solely on expensive expert labor doing one tape at a time.       



Allan McConnell  








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