Quad Heads--When metal tips gave way to Ferrite... and what role Spin Physics played--

[Ted Langdell]

While looking for something else, we found an interesting patent that outlines problems and solutions to interchanging tapes made with metal (Alfasil) or ferrite heads.

Issued late in the Quad game, (1980s') this patent http://www.google.com/patents/US4398226, the invention enabled the use of ferrite heads to record a signal similar to that of metal heads so the playback on a metal-head wouldn't require readjustment of EQ.

"With the equalization of a quadruplex recorder adjusted to accommodate the new ferrite heads, it happens that tapes, pre-recorded by use of metal heads, are productive during video playback of color over-saturation. It would, of course, be possible to adjust (or readjust as the case may be) a quadruplex recorder depending on whether it was reproducing signals recorded by means of metal heads or by means of the new ferrite heads. But such a tack is not too practical when, for example, tapes produced by means of metal heads are interspersedly spliced to tapes produced by means of ferrite heads. Consider, for example, that a pre-recorded commercial made by use of a quadruplex recorder having metal heads is to be spliced into a taped TV program made by means of a recorder having ferrite heads. In such a case, either the playback electronics will have to be optimized for good playback (and thus broadcasting) of either, but not both, the commercial or the program."

"...the concept of the invention is to mount corrective attenuation circuit(s) directly to the quadruplex head assembly, such circuits being of a type which self-disable during signal playback. Thus, no alteration ever need be made to the quadruplex recorder to effect a uniform standard for the level of recorded flux, regardless of the nature of the head employed. Head assemblies employing metal heads will record a certain way . . . and head assemblies equipped with ferrite heads (plus the corrective attenuation circuit) will record that very same way. During playback, however, the improved efficiency of ferrite heads vis-a-vis metal heads is brought to bear as the corrective circuits cut out. There is, pursuant to the invention, virtually no difference between recordings made by quadruplex head assemblies equipped with metal heads or with ferrite heads, so long as the corrective circuits are employed. As far as the user is concerned, and except for the long life provided by ferrite heads, he could not care less whether his recordings were by metal or ferrite heads since all such recordings are all essentially identical, and playback is the same."

At one time, Spin Physics was one of several companies refurbishing Quad heads, and engaging in R&D in other areas of magnetic recording and playback involving other media formats.

Spin Physics was founded 1968 by James Lemke, PhD and was sold to Eastman Kodak in 1972. (Hence Kodak appearing in the patent list here: http://www.plainsite.org/flashlight/spin-physics-inc/page-1/table-patents)

In August, 2000, San Diego based Spin Phyics sold Prodex—its BetacamSP head replacement business—to Palo Alto based Quad head refurbisher Videomax, headed by Bill Fitts.

By 2001, the Spin Physics website noted it was making more than "2,000 models of magnetic tape heads, supporting virtually every make of high-end recorder in worldwide commercial, OEM, government and aerospace markets throughout the world," according to its website, captured by Archive.org's Wayback Machine: https://web.archive.org/web/20010301080630/http://www.spinphysics.com/

It was building a motion analysis system noted here:
http://machinedesign.com/engineering-education/looking-back-232011

Spin Physics Milestones were listed here: 
https://web.archive.org/web/20010220054542/http://www.spinphysics.com/Press/MileStones.shtml

A mid-2001 website redesign using Flash rendered the content after that unrecovered by Archive.org, and by March of 2004 the domain was for sale.

What do you remember about Spin Physics?

Ted

Ted Langdell
Secretary
Quad Videotape Group
e-mail:	ted at quadvideotapegroup.com

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