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Re: HD vtrs
- To: Jimwheeler at aol.com
- Subject: Re: HD vtrs
- From: Rob Lingelbach <rob at alegria.com>
- Date: Wed, 30 Jun 1999 23:18:12 -0500
- Cc: telecine internet group <telecine at alegria.com>
- In-Reply-To: <b7bc7efa.24abfa84 at aol.com>; from Jimwheeler at aol.com on Wed, Jun 30, 1999 at 05:57:12PM -0500
- Mail-Followup-To: Jimwheeler at aol.com,telecine internet group <telecine at alegria.com>
- References: <b7bc7efa.24abfa84 at aol.com>
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the following I am forwarding to the TIG as it was sent by a
On 1999-06-30 at 17:57, Jimwheeler at aol.com (Jimwheeler at aol.com) wrote:
A friend of mine on your List sent me a copy of the message from Mike Parsons
about the A, B, and C formats.
I retired as an Ampex engineer in 1993 after 32 years at Ampex. I am now a
consultant about tape, tape formats, and archival issues with tape and discs.
I am a technical advisor for the Nixon White House tapes project and I work
for NASA, Library of Congress, National Archives, etc.
I was involved in developing both the A and the C formats. Also, I am
co-inventor of the AST.
First of all, Alex Maxey invented the quad, helical, A and B formats. An
As for Sony killing B, I think it had a lot more to do with Ampex. All tv
stations worldwide were Ampex (or RCA) customers at that time and the
decision to go A format (later C) was more a question of client loyalty than
any insidious marketing hype. That Sony and Ampex came to a common standard
with C format was more a part of Sony hoping to leap on the Ampex bandwagon
than any need by Ampex to acquire overseas technology.
I agree except it wasn't Ampex and Sony per se--it was SMPTE and ABC/CBS.
Ampex introduced the VPR-1 (A format with AST) at the Chicago NAB in 1976 and
Sony was at the same NAB (for the first time) with a one inch machine. ABC
and CBS did not like the idea of two formats so they wrote a letter to SMPTE
asking that a standards committe be formed to come up with a Compromise.
This was new role for SMPTE. SMPTE had adopted the various quad formats as
SMPTE standards but now there were several new formats. It was decided to
call the Ampex helical the "A" format, the Bosch format "B", and the new
compromise format "C". I was aked to specify the "A" format and said that it
was impossible. As Dale Dolby put it, "There are 30,000 A machines out there
and that meansthere are 30,000 formats". The old Ampex "A" machines were
terrible for interchange! Around 1972/1973, I was asked to analyze the "A"
format interchange problem. I concluded that it was complex and involved the
scanner surface finish, capstan, the movable guides, and the weak top plate.
That's when a genius mechanical engineer (Dick Hathaway) came up with a
solution for the capstan, guides, and top plate. I came up with a solution
for the scanner problem. Dick also conceived the AST while on a vacation in
Canada. I took Dick's idea and made it into a usable product on a VPR-7950.
Ampex marketing did not like it because the AST could hurt our "Bread and
Butter"--the quad. Art Hausman and Charlie Steinberg over-ruled marketing
and the VPR-1 was born. The code name was "THOR-2". this confused Sony
because they thought that THOR-2 was just another version of THOR. I was
responsible for THOR and that was just an upgrade of the VPR-5800--a type A
machine. That's why Sony was so shocked at the '76 NAB Convention.
In fact, C format was just about identical to A format with a slight change
to the head angle. A format tapes will spool in vision on a C format machine
and vice versa. So small were the differences between A and C that Ampex
retrofitted almost all VPR1s to be C format and these workhorse VTRs were in
service at least as long as the vpr2bs that replaced them.
The C format was totally different! The upper drum on the C is larger
because of the need for downward bias on the band guide. The A format had a
very unstable "S' shape helical track. The C format was a very straight
track--because of the band guide. The A format could not play/record
simultaneously because it only had one record/play head. The C format had a
separate record head and play head--a totally new concept for video tape
recorders! The C format has sync heads that recorded vertical sync during
the time that the video head was off tape. This was CRITICAL to meet FCC
standards! There were several other differences but these were the main ones.
As to whether the technical spec was inferior or not, the VPR1 put probably
some of the straightest lines on tape and had a very high rf envelope due in
part to the ast head but also the high mechanical tolerances through the
The reason for the straight tracks was that the VPR-1 had a very stiff top
plate and the scanner had a very low friction. The AST helped but the tape
had a higher coercivity. Memorex had developed a tape with about 500
oersteds vs the previous 320 oersteds. I worked very closely with Memorex
engineers to make this happen.
The B format and C format machines had near identical spec in terms of
bandwidth but the B formats alone exhibited some of the problems encountered
with Quad machines in terms of head - segment misalignment.
1978 was a bad year to be a facility buying vtrs. There was no right choice.
Quad was clearly dead, 2 inch Helical IVC 9000 was great technically but no
more financially viable than Quad, 1" A and 1" B were both doomed a year
later. The best choice was 1"A as at least it could be upgraded to C. But I
think the lesson here is that history shows that we should be very cautious
before leaping and seeing HDcam and D5-HD as "neccesary interim formats".
It's a totally different world now so no one can predict the trend. We no
longer have a strong ABC, CBS. NBC. We no longer have Ampex. We no longer
have the expensive formats dominating the market. A new ball game! Two
companies make videotape recorders (Matshushita and Sony) and they do what
Rob Lingelbach "I would give nothing for that man's religion
rob at alegria.com whose very dog and cat are not the better for it."
http://www.alegria.com --Abraham Lincoln
Thanks to Rich Torpey for support in 1999
No advertising/marketing allowed on the main TIG. Contact rob at alegria.com
anonymous messaging now at http://www.alegria.com/HyperNews/get/ubique.html
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