|
|
This topic comprises 4 pages: 1 2 3 4
|
|
Author
|
Topic: Perspect-A-Card
|
|
|
Steve Guttag
We forgot the crackers Gromit!!!
Posts: 12814
From: Annapolis, MD
Registered: Dec 1999
|
posted 10-29-2008 07:32 PM
Everything is possible with the CP200!
There would indeed be a bit of work involved. It wouldn't be the end of the world to get one of the available sockets to work...infact, Dolby devised a way for inboard surround-EX to do just that....a Cat 150 is mounted in the Aux rack with a logic card. The mod (I've done two) takes less than an hour to do. They used the slots for the never used mid-p and mid-q delay boards.
The trick then is to get the audio back in and switched (and at the right level). The level part is easy to deal with via resistors...the output of a Cat 150 is 500mV...the CP200 runs on 300mV buss levels.
To be real slick...I ask...do you use your mic? If so, do you play it through the stage channels (and get feed back)? If the answer is no to either question... It is possible to bring the Perspecta decoded signal back through the mic inputs on the Cat 141 in SK16.
Remove the jumper for Mic-Center and discard.
Connect the Left signal to A22, the Center signal to B4 and the Right signal to B23. Program Cat 153 Opt for the "Non-Sync Mic" control on your desired format number.
So you want to use the funky surround thing too? No problem because you are going to need to silence the mic that would be feeding the surround since you are going to have to use the Non-Sync Mic control line (aka control line 18) to select LCR.
On the next Cat 141A (Slote SK18) the surrounds can be picked up. Connect the signal to B4 and B8...then also program Optical Stereo surround (I believe the Flow Chart is incorrect in calling for Future 5 here). If you have any Cat 150s kicking around that were made of two boards...separate them and use the delay board in the Acc rack to delay the surrounds...again, some mods are likely needed (I haven't thought it out that far) but I'm telling you, damn near anything is possible, sound wise, with the CP200. By far, the best designed processer for cinema, ever. Its only real major design flaw, in my opinion, was having the subwoofer output come from the Processing unit rather than have the signal flow down with the rest of the outputs. It would have given the Cat 137 a little more to do than just be a line amp card and made the whole JM11/21 thing a bit cleaner when the digitals came along....but Christ it was designed in the late '70s!!! Not bad for processor that came out 28-years ago.
Steve
| IP: Logged
|
|
|
|
Stephen Furley
Film God
Posts: 3059
From: Coulsdon, Croydon, England
Registered: May 2002
|
posted 10-30-2008 04:00 AM
How do you kill he NR on a 65? I've done it by removing the cards and attaching jumper connections to the backplane via croc clips, but that was only for a few minutes use to demonstrate the process. There's got to be a better way, should be possible to install a switch to short or open some diodes, if I knew which ones.
quote: Mitchell Dvoskin
Do these cards have the capability to be calibrated? If so, is calibration film available? I know that actual Perspecta Intergrators from the 1950's requrired calibration from test tone control film, much as analog Dolby stereo needs calibration. Each of the control tones needs to be calibrated for the correct volume level.
Mitchell, I will send you a private message later today.
I think there are two issues here. Firstly, there is the tuning of the filters in the integrator to match the tone frequencies being received frpm the optical pre-amp, Steve has largely dealt with this. Secondly, there is the question of equalisation of the signal to ensure the corect amplitude of sound in each of the three channels. Obviously, if the equalisation of the signal at the bottom end is wrong then this will affect the amplitude of the tones, and therefore of the sound fed to each output channel. All I can say is that when I had my card I didn't have to adjust anything, and it sounded ok. I think there are some presets on the card, but I didn't touch them.
The card is almost all discrete components, and there are a lot of them; it's a very full card.
Dion calibrates the cards themselves using electromically generated tones, of course, this ensures correct levels within the card itself only if the correct levels are being fed into it, and the only way to ensure this is to play calibrated test tones from film on the actual soundheads to be used, and obviously he cannot do this without visiting the actual installation. He has an original Perspecta test/demo film which he plays at his 'Fantasic Fomats' lectures, an I believe he does normally test the cards with this, though obviously not on the actual installation to be used, so the levels of the tones beinf fed to the card must be in question. I received a note from Susan saying that my card had not been tested with film as the test film was in Norway at the time. It sounded fine to me when I used it. I suppose stictly speaking the system should be calibrated to correct for any inbalance of the equalisation of the signal at the bottom end, but I didn't have the means to do this, and it didn't seem to be necessary. It should be possible to get a lab to record a test film with a few seconds of each of 30, 35 an 40 Hz. tone at calibrated equal amplitude if you wanted to, but I had no problems with any audible inbalance between the channels.
I have heard 'Forbidden Planet' through the original integrator at the Loew's Jersey in 2002, and the first few minutes of it through one of the modern cards at Bradford in 2005. I had to leave at that point to catch the last train back to London. Obviously, hearing the two devices in two different auditoria, and almost three years apart is not the ideal way to compare them, but the results sounded pretty similar to me. I don't know if Dion carried out any calibration of the installation at Bradford before this show. Of course, what is really needed is to use a cinema with both types of equipment installed, and to switch between the two to compare them. Unfortunately, I have only ever seen two original integrators, one in England which hadn't been used in decades, was in poor condition and had lots of hum, and the one at the Loew's Jersey, which didn't have a processor which could take the modern card, so such a comparison wasn't possible.
The only material I have played through my own card is a couple of minutes of an unknown feature and a few cartoons. This was the only material which I was able to obtain, and was used simply to demonstate the process.
Something Dion did mention at Bradford was the possibility that the magnetic track for the 35mm version of 'Around the World in 80 Days' which used Perspecta on the surround channel still exists, and might be played at a future Widescreen Weekend. I've heard nothing since, but I was not at the 2006 or 2007 events. I would be very interested to hear this track, which was used on both 35mm 4-track mag prints, and I believe of the sep-mag track which ran with the infamous 34mm print in London. There is a photograph which certainly shows an Integrator in that installation. This needed a modified integrator, but details of the modification exist, and i shouldn't be difficult to do; I think the main difference was that when no tones were present the signal was fed to all three output channels, rather than none of them, as it would be with conventional Perspecta.
[ 10-30-2008, 05:16 AM: Message edited by: Stephen Furley ]
| IP: Logged
|
|
|
|
Stephen Furley
Film God
Posts: 3059
From: Coulsdon, Croydon, England
Registered: May 2002
|
posted 10-30-2008 04:22 PM
When I bought my card they were 300 pounds. This is also the price which was printed on a leaflet which was available at the time. I don't know if the cards are still available, nor what the price is now if they are.
The cards were very professionally made, looked exactly like a mass produced card. Considering the small number involved, I think Dion said that he sold about 30, I'm surprised that he was able to have even the blank cards produced for that cost, never mind buying the several hundred components and hand-soldering them all in place, and testing the finished cards. I think the price was a real bargain.
I would guess that most of the cost for the production of the cards was the setting-up cost, so Dion may well have ordered more of them than he thought he'd need, so he may still have some in stock. From memory, I think all of the components were readily available standard ones, so if he does still have any blank cards in stock it would be possible to build more, if he has the time available to do it, and is willing to do so. The production of these cards certainly cannot have been a money spinning exercise.
| IP: Logged
|
|
|
|
Stephen Furley
Film God
Posts: 3059
From: Coulsdon, Croydon, England
Registered: May 2002
|
posted 10-31-2008 04:22 AM
I'm pretty ure 'Forbidden Planet' was released in both 4-track and Perspecta. Prints of 'White Christmas' with mag stripes on them also existed, but whether they were from the original release, or were made later, I don't know. I also don't know what was recorded on the stripes since the cinema I saw it in was only equipped for mono optical, it could have been a full 3 or 4 channel stereo mix, or the Perspecta track decoded and recorded on three channels, as is sometimes done with DVDs today, or mono recorded on the centre channel only, or mono recorded on all three of the screen channels. I don't even know if the print carried all 4 stripes, since I didn't actually see it, but the projectionist told me that it was a mag-optical print, and remarked that it was a pity that he could only run it in mono optical.
Something else which Dion told me about his Perspecta cards was that he had supplied one to a company who were going to use it to convert Perspecta tracks to Dolby Digital, for use on DVDs, as mentioned above. This was for Japanese films, but I cannot remember the title of the one which had been released.
There were also rumors that the mono French track on the 'Forbidden Planet' DVD was actually in Perspecta, with the tones intact. I borrowed a copy of the DVD from somebody, and tried putting it through the Perspecta card; there were certainly no Perspecta tones on the copy that I tried. There has been more than one DVD release of this film, so it's possible that another version may have had it, but I'm skeptical.
| IP: Logged
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
All times are Central (GMT -6:00)
|
This topic comprises 4 pages: 1 2 3 4
|
Powered by Infopop Corporation
UBB.classicTM
6.3.1.2
The Film-Tech Forums are designed for various members related to the cinema industry to express their opinions, viewpoints and testimonials on various products, services and events based upon speculation, personal knowledge and factual information through use, therefore all views represented here allow no liability upon the publishers of this web site and the owners of said views assume no liability for any ill will resulting from these postings. The posts made here are for educational as well as entertainment purposes and as such anyone viewing this portion of the website must accept these views as statements of the author of that opinion
and agrees to release the authors from any and all liability.
|
Home
Printer-friendly view of this topic