Film-Tech Forum ARCHIVE: Cat 702??

This is topic Cat 702?? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Ken Lackner (Member # 1002) on 01-05-2003, 09:20 AM:

Dolby has a Cat 702 soundhead on their website. It looks the same as the 701. How is it different?

Posted by Jean-Michel Grin (Member # 1360) on 01-05-2003, 10:08 AM:

Maybe the red Led illumination device ?

Posted by Richard Fowler (Member # 893) on 01-05-2003, 10:12 AM:

It is like the BACP/USL penthouse since the 702 does not require an internal power supply and cord....the power for the LED and pre-amplifier is tapped from the voltage rails from the digital cable...a sharing of technology even if they do not publicly admit the source [Wink]

Posted by Steve Guttag (Member # 268) on 01-05-2003, 10:24 AM:

Another "borrowed" idea is that it has "go/nogo" LEDs that are visible through the cover to indicate if the LED level is sufficient

Steve

Posted by Mark Gulbrandsen (Member # 72) on 01-05-2003, 10:27 AM:

Indeed, you are right. Dolby reportedly made a deal with Jack Cashin to use the design as well as some of Jacks Light meter stuff in the 650 to make it track SRD better. Of course, Dolby has to be at least a tiny bit competitive to be able to sell product.....
Mark @ CLACO

Posted by Gordon McLeod (Member # 33) on 01-05-2003, 11:35 AM:

To bad USL/BACP never followed through with the original idea of their penthouse having the both SRD pickup and a DTS timecode reader allon the same unit

Posted by Mark Gulbrandsen (Member # 72) on 01-05-2003, 12:14 PM:

I wonder if thats covered by some still valid DTS patent?
Mark

Posted by Christos Mitsakis (Member # 143) on 01-05-2003, 02:02 PM:

So has the time come for Cat701 to pass to history?
As I understand, for some time Dolby will have both in catalogue. If you have to choose now a penthouse DD head which of the two would you choose 701 or 702? Or should you also consider USL/BACP?
Indeed, less wires the better, but I have to say that I am happy with Cat700 and 701.

Christos

Posted by Steve Guttag (Member # 268) on 01-05-2003, 04:06 PM:

I think the 701 is history. In a free marketplace, you should always feel free to chose whomever's product you feel gives you the best value/performance.

As to the lack of DTS...the rumor was to having the Dolby license (and hence, supply of the CCD board) they couldn't make a combo reader. If the rumor is true, it was a dumb stipulation since if someone was to buy the reader, they would have a Dolby Digital system in there anyway.

Steve

Posted by Ken Lackner (Member # 1002) on 01-05-2003, 04:18 PM:

What is USL/BACP?

Posted by Gordon McLeod (Member # 33) on 01-05-2003, 04:27 PM:

USL= Ultra Stereo Labs
BACP= Bay Area Cinema Products

Posted by Richard Fowler (Member # 893) on 01-05-2003, 04:28 PM:

BACP is Bay Area Cinema Products, which is run by Sam Chavez who until the early 1990's did cinema marketing for Dolby. He is one of the key people who pushed the LED reverse scan idea which is now common. After leaving Dolby he was for a while at Component Engineering before setting up BACP. USL is Ultra Stereo Labs which manufacture BACP product in a joint partnership with Jack Cashin, the only other man to get an Academy Award for optical sound improvement in addition to Ray Dolby. [Wink]

Posted by Rick Long (Member # 213) on 01-06-2003, 12:44 AM:

Sorry, slightly off topic but....

I did a search for this, honest, but couldn't find the answer. Anyways this seemed like a good as any topic to dump this in.

I have a few 701's which do not give out the required level (this after led power supply adjustment). This causes me to think that the l.e.d.'s are a little old. Are these l.e.d.'s field replaceable?

A few other units have failed also giving no output whatsoever, causing me to think the CCD board has failed. I notice that the CCD itself is installed in a socket. Is the CCD the likely suspect and if so, can it be replaced in the field or should the whole board be replaced?

Out of desparation, I tried putting a CCD board from a 701 into a 700 sound-head. I had to reduce the links to the X1 position to drop the signal level, but it seemed to work ok although there did seem to be a little resistance to dropping to SR on the loop splice.

I should mention that these tests were all done in a shop with the same Dolby (CP-500) test jig.

Thanks in advance, for any help.

Posted by Steve Guttag (Member # 268) on 01-06-2003, 07:57 AM:

The RED LEDs have dimmed to the point of being unusable. God you just gotta love the visible red LEDs...more unstable than an exciter lamp at seven times the price!

The LEDs are field changeable. The LED itself is available (you'll need to be handy with a soldering iron) or by changing the whole head assembly out.

Steve

Posted by Rick Long (Member # 213) on 01-06-2003, 09:12 AM:

Thank you, Steve. Warming up my 100-watt American Beauty as we speak. [Wink]

Posted by Brad Miller (Member # 2) on 01-06-2003, 09:22 AM:

I'm with you Steve, I wish Dolby would go back to the cat 699/700 bulb. I've got a cat 701 in a theater that only runs evening shows and is already maxed out after about 2 years. (I should specify that this is the only 701 I have seen require maxing on the supply in such a short amount of time though.) It still tracks good, but was recently faulting and when I realigned it I had to max it out to achieve level. How much time do you think it has left?

On the flip side, I have one of the older style penthouses (can't remember if it was a 699 or 700) at another theater that has been running for 2-3 years on the same bulb. The thing still reads at 0-1, so I'm not going to change it until I see the error count increase or the thing dies! When it does finally go, it will take the projectionist there a whopping 2 minutes to handle it. [Smile]

Posted by Steve Guttag (Member # 268) on 01-06-2003, 11:31 AM:

One of the many issues with the visible red LEDs is that they are unpredictable...some fade fast...others are marathon runners.

For a penthouse reader...the choice is obvious, the conventional exciter lamp is the only smart choice...the CCD doesn't do as well with the monochromatic light source and the stability of the LEDs down right suck. The switch from the 700 to the 701 defies any sort of logic unless you had an agenda to sell more LEDs...hmmmmm

Steve

Posted by Ken Lackner (Member # 1002) on 01-06-2003, 04:31 PM:

I take it from your discussion and preference towards the cat 699/700, that red LED's are not going to be necessary with digital tracks as they are with the optical track? If that's the case, why did they even switch?

Posted by Steve Guttag (Member # 268) on 01-06-2003, 05:15 PM:

There is NO good reason to have switched the digital reader lamp whatsoever. Just bad engineering at work and possible red LED agenda going on....Dolby doesn't get to sell you EPT lamps every two years the way they get to sell you their red LED.

Do you REALLY believe that the cyan tracks are going to come this year or ever? Red LEDs aren't going to be needed for the analog sound either.

I've said it before and I'll say it again...cyan tracks are a dumb idea whose only hopes are to offer the industry inferior quality.

Steve

Posted by Steve Kraus (Member # 476) on 01-06-2003, 05:57 PM:

What was the difference between the 699 and the 700? Both were halogen lamps, no? And 701 and 702 are red LED with just a difference in power source? Has the CCD and optics been the same all along?

Posted by Mark Gulbrandsen (Member # 72) on 01-06-2003, 07:58 PM:

Steve K, I believe that both the lamp power supplies and the ccd end of things were much more complicated in the 699....all vastly simplified in the 700 for the mass market.
I still prefer the white light cat 700 over any of the scanners out there. Who the heck buys their EPT lamps from Dolby?????? That is a pretty common lamp available fomr many lamp wholsalers for about half of their price. Never had any poor results with doing it the cheaper way.
MArk @ CLACO

Posted by Steve Guttag (Member # 268) on 01-06-2003, 09:33 PM:

The CCD has been the same up until the late model Cat 701 and then Cat 702...it is more sensitive to allow lower LED current to allow yet longer life.

As to the Cat. 699...it used a different lamp than the Cat. 700. The Cat. 699 lamp was a single source lamp too...Gilway. I believe it was 12V versus the EPT's 10.8. The EPT is a more common lamp (even has the ANSI code to it).

The Cat. 699 used fixed precision machining for alignment of the optical path...the Cat. 700 was less precise but allow you to adjust the CCD board to get things near perfect. The Cat. 699 had a better film path and superior damping, in my opinon. The Cat 700 had a much better flywheel than the Cat. 699. If the Cat. 699 had the more massive flywheel it would track even better.

Steve

Posted by Ken Lackner (Member # 1002) on 01-07-2003, 07:50 AM:

quote:
Do you REALLY believe that the cyan tracks are going to come this year or ever? Red LEDs aren't going to be needed for the analog sound either.

I've said it before and I'll say it again...cyan tracks are a dumb idea whose only hopes are to offer the industry inferior quality.

OK. Let's assume the cyan tracks will happen someday. My question is, are the red readers only necessary for the optical track, or at that point will they be needed for the digital tracks as well?

Posted by John Pytlak (Member # 331) on 01-07-2003, 09:33 AM:

Both the Dolby Digital and SDDS digital tracks are normally printed with DYE images, with no silver redevelopment required, since the readers (tungsten or red LED sources) were designed to read dye images. They don't depend on having silver in the image like tungsten lamp analog readers. Cyan dye analog tracks eliminate the need for redevelopment of the soundtrack area, and leave NO silver in the track, and will require a red LED reader:

http://www.dyetracks.org

http://www.kodak.com/US/en/motion/support/dyetrack.shtml

Posted by Christopher Seo (Member # 7) on 01-07-2003, 11:01 AM:

Ken brings up an interesting point. Why is it that tungsten lamps are fine for dye-only digital tracks but not for dye-only analog tracks? Are the digital reader CCDs insensitive to the lamp's infrared, where solar cells are susceptible?

Posted by John Pytlak (Member # 331) on 01-07-2003, 11:19 AM:

I'm not sure of the spectral response of the particular photoreceptors used for the digital readers, but the photocells in most analog readers have significant sensitivity in the infrared portion of the spectrum, where film dyes absorb little energy. Using a high intensity red (LED) light source puts the peak reader sensitivity right at the peak spectral density of the cyan dye, even with a cell that "sees" infrared energy (e.g., S-1 response peaks at 800 nanometres). Even so, noise is typically higher, requiring effective noise reduction like Dolby SR.

There are cells sensitive to mostly visible light (e.g., S-4 sensivity curve peaks at 400 nanometres with almost no IR sensitivity), but they have much less quantum efficiency than the S-1 response cells. So noise becomes even more of an issue.

It's likely that for a digital reader, where you are just trying to discern "on" and "off" bits, the quantum noise of the detector is not as much of an issue as with analog sound. So a CCD sensitive to visible light can be used with either a red LED or a tungsten light source, and easily discern bit images made of only dye.

Information on photodetectors:

http://www.cem.msu.edu/~cem835/Lecture04.pdf

Posted by Steve Guttag (Member # 268) on 01-07-2003, 04:10 PM:

With digital, you are looking for a distinct level difference, at one point a digial processer will declare a level high or low...not somewhere in between. If you hook up the Dolby DRAS program and look at the "Histogram" section you will see it has two camel like humps. the left one is where the bright bits are the right one is where the dark bits are.

The CCD is actually too sensitive to UV...all of the readers that have white light exciter lamps on them have UV filters right in front of the lamp.

If you look at the histogram of a RED light reader you will see it has trouble deciding on the right "hump"...it never really peaks.

Steve