Dolby Digital Reader

[Adam Liberman]

What are the differences/improvements between the Dolby CAT 700, 701, and 702 digital readers?

[Josh Jones]

699/700 had halogen illumination. The Cat 701 and 702 were LED. The 702 was powered by the processor, no external power connection required, like the BACP penthouse. The 700 usually had 70/35mm bypass rollers.

[Christos Gartaganis]

The cat.702 also features an improved version of the digital reader board, which offers greater sensitivity compared to its predecessors. This improvement helps extend the lifespan of the red LED by lowering its operating current to below 80 mA.

[Jim Cassedy]

The Cat 700's also had a power switch on the front so that you could turn them off when
not being used. I occasionally do contract work at one venue that will uses a CP650 as
their main processor, but they only run film several times a year. That meant that for
most of the year, they would be putting hours on the Dolby Digital reader bulbs any
time the CP650 was powered up for other events.

[Adam Liberman]

1) Are the analog/digital basement readers (such as the Kelmar) just a low-cost alternative to the Dolby 699-702 penthouse readers? I'd assume that the issues with them would be the minimal delay time for analog fallback, and poorer stability since they lack the Davis loop transport of the penthouse readers.

2) Why does Dolby describe the DA20 being used with the CP500, since the CP500 already has Dolby Digital with the delay built in?

[Tj Hopland]

There isn't really a clear answer which was better as far as basement or penthouse. Its like everything else you had to make up your own pros and cons list and then pick what would have been the best fit at the time. There were times and situations were one really made sense over the other one but you move a year or two later and maybe it flips. Or change projector models and it flips again. Maybe you started retrofitting to stadium seating and having to raise the projectors on a platform? Having the top roller 6" lower could have advantages.

Some of the basement brands in some projector brands were as or more reliable and stable as the penthouses while others tended to drift and need alignment more often. Alignment on the basements could be a lot of work since you are having to get both analog and digital aligned at basically the same point on the film so messing with one could mess up the other especially if there was people messing with things since on some systems there wasn't really any fixed reference point to start from.


As to why they talk about the CP500 and DA20 together? I really don't know it would have been a pretty limited use case, maybe a mobile setup? But back then Dolby did often think of an have a plan for those kinda fringe cases which was really nice if you were one of those cases. And by mobile I mean that in the earlier days of digital film sound besides the hardware being relatively expensive there were the usual format wars stuff going on. Different studios would tend to favor or maybe be exclusive to one format. Guess which studio did SDDS? Universal did DTS.

So if you stuck a fully loaded CP500 in your big screen and wanted to play the big Universal picture in there and wanted in digital sound you need DTS. This may be a case where the basement reader would be good if you were expecting mostly SRD and just the occasional DTS or SDDS title on that screen. Smaller stack and less complex film path if you don't also have the SRD penthouse up there. But then remember cost and that theater owners have always been cheap on some level?

Companies like Kelmar made 'docking plates' which was a quick change mounting system for penthouse readers, any of the 3. They would also still hold the rollers in place so you didn't need any penthouse in place. Others like Odyssey made rack panels with jacks and mode switches you put in your rack near your CP and then you had a little rack with wheels with your DA20 or whatever in it with the reader attached on its docking plate and you just wheeled it to what ever screen you needed it on based on what movie was playing at the time. This meant you had 3 screens and happened to be playing a Columbia, Universal, and Disney film all 3 screens could be in digital and you only had to own 3 systems.

So maybe you had a CP500 SR which was the version without the SRD cards and then you had the mobile cart setup? Like I said pretty limited use case but I'm sure it happened. If the mobile thing was really your plan that you thought was going to be long term you could have probably bought a CP65 for less than the CP500SR but I think a lot of people expected that the format war would not last that long (which it didn't) and then they could just get the upgrade kit for their 500 and have a nice clean setup. Since most of the boards were the same you could even pull cards out of the DA20 but for most people they could find another screen with say a CP65 or other CP to permanently mount their formerly mobile DA20 in rather than parting it out to upgrade a 500.

[Randy Stankey]

Some of the basement brands in some projector brands were as or more reliable and stable as the penthouses

IMO, penthouse readers require just a bit of back tension on the film to keep them stable. If the film bounces too much, the reader can't track as well.
I used a BACP reader that, if you put an extra roller in the path, upstream of the reader, that tiny bit of tension would help the reader track much better. I've seen the very same reel of film track 5's and 6's without back tension and 3's or 4's with back tension.

With the Kelmar basemet readers, if you set them up right, they'll track 0's and 1's all day long. The film tension at the impedance drum is much more constant and predictable than any penthouse reader can have. However, as you say, they do require upkeep. If you don't keep them aligned and calibrated, they can and will spite you. Then, again, aren't you supposed to keep on your PM's?

[Ryan Gallagher]

We saw some 0-1s error rate with our 702s on a new CineLab print during our recent festival. Best I've seen in this booth, but we typically don't run brand new prints either. We don't have an extra roller above them. Our feed tension range with a 15" Goldberg 8 hole reel are between 0.7N (full), and 2.5N (empty).

[David Ferguson]

The best I’ve ever seen was a “0” on my home setup, and that was on a 12 year old print, that in some sections looks like it has been dragged across a floor. I was astounded, but this was after a few passes of FilmGuard.

For the difference between readers, I seem to remember there were differences in flywheel sizes, but maybe someone can confirm or reject that.