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Re: HD vtrs



the following I am forwarding to the TIG as it was sent by a
non-subscriber.

--Rob
TIG admin

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 
incredible person.  


Mike said:
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 
heads. 

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.

I agree.  


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 
they want!

Jim Wheeler


-- 
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

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