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MMD > Archives > December 1996 > 1996.12.06 > 13Prev  Next

Re: Replicating Punched Paper
By Karl Petersen

The perforator advance rate seems to be less critical than the relative positions of the perforations in time. Naturally it is of critical concern when reading a roll for re-mastering or accurately duplicating since you want to stay perfectly in sync.

[ Caution, Karl! _Time_ has nothing to do with replicating a paper roll;
[ the problem is the critical _spatial_ positions of the perforations.
[ -- Robbie

If you ran your master through the machine and set your perforator cam at a higher or lower ratio you would get the notes and code holes to start at the same time and leave off at the same time, relatively speaking, by changing the playing tempo slightly. The exception would be the apparent hole elongation or delay in closing of each signal. This could cause a problem with Welte, but I think it would be less concern on the other systems. Did they simply use higher tempos for recording where code changes occurred so close behind one another that the apparent delayed closures would cause smearing of accents?

[ Ampico issued rolls with tempos marked anywhere from Tempo 50 to Tempo
[ 120. They evidently were quite concerned about closely-spaced notes
[ and intensity commands. On the contrary, Welte (Freiburg) evidently
[ assumed that their high-resolution asynchronous production perforator
[ was precise enough to maintain the spatial accuracy needed in the
[ copies. I'm not convinced their assumption was correct!
[ -- Robbie

If you had a tracker bar with holes half as long in the direction of roll travel and a punch that made holes half as long in the direction of travel, then you could run all your rolls at half speed and save lots of paper.

Undersized holes are a real problem. Many Klavier rolls from the 1960s were defective in this way. I disagree that the exact diameter is the most critical element.

Robbie's treatise on the machinist's view certainly defines the mechanical needs in a mechanical (system) context and shows how they are independent of the music (data), as they must be in order to preserve the integrity of the music.

Defining the requirements and thereby the acceptance criteria is the greatest task because all factors in the equation must be recognized and defined. Often this is done by iteration, much to the consternation of the person who runs through the exercise a dozen times, adding the New Factor with each pass.

[ I can tell that you've spent many hours at this paperwork, Karl,
[ but the cost of your time spent discussing the "New Factor" is
[ far less than the cost of re-doing the hardware when the "New
[ Factor" is discovered during the Acceptance Test! -- Robbie

On with the work!

Karl A. Petersen
Meridian, Idaho

(Message sent Sat 7 Dec 1996, 02:56:05 GMT, from time zone GMT-0700.)

Key Words in Subject:  Paper, Punched, Replicating

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