Film-Tech Forum ARCHIVE: Connecting DVD to CP-55

This is topic Connecting DVD to CP-55 in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=002706

Posted by Neil Chue Hong (Member # 685) on 10-08-2001, 08:15 AM:

Hi,

a couple of quick questions...

I'd like to connect a DVD player to our Dolby CP-55 (with SRA-5) so that the sound from the player is processed through the matrix.

Q1) Will this work? (is there a difference in the matrix between Dolby on DVDs, and Dolby on film?)

Q2) Where do I connect it? The non-sync L/R input appears not to process the sound - should it? From the manuals, it appears that the aux input requires a separate processor to split it into L/C/R/S first.

Over to the experts!

Posted by Steve Guttag (Member # 268) on 10-08-2001, 09:21 AM:

Though I haven't had to do such a thing yet...

On a CP-55 with an SRA-5 SR adapter...presumming you have installed it the current method (the SRA-5 connects to the DT inputs on the backplane of the CP-55 and format 03's button is now the format 05 (SR)) I would have the DVD player come in through the SRA-5's Non-Sync inputs and switch the SRA-5 between Non-Sync and film...you will need to select "SR" still to have the CP-55 look at the SRA-5 as the source but otherwise it should work...watch your levels though.

Steve

------------------
"Old projectionists never die, they just changeover!"

Posted by Michael Brown (Member # 890) on 10-08-2001, 12:18 PM:

Doesn't a dvd output in Dolby surround and a cp-55 decode Dolby stereo?

Posted by Pete Naples (Member # 761) on 10-08-2001, 02:48 PM:

Steve, I have recently done exactly this in two screens at a local cinema and it works a treat.
Connect the DVD O/P to the non-sync L-R I/P on the SRA5. I fitted a little toggle switch to switch the SRA5 into non-sync and out of SR. Had to turn the non-sync level pot full up to get any sensible output level.
I set the DVD players audio output to 'Dolby Digital 2 channel", which is Pro-Logic, it really does sound quite nice.

Neil, when did EUFS get Dolby?? Why didn't I install it??? Hmmm??? Support your local engineer!

Michael, I think you have your terminology a little confused. The CP55 is 4.1, more commonly known as Dolby Stereo, in it's native state it decodes L,C,R with or without surround, with A type noise reduction. With the addition of an SRA5 it can decode Dolby SR prints. The best way to connect the SRA5 involves some backplane mods and re-programming the 03 Dolby Stero Without Surround button to be 05 Dolby SR.

With the DVD player I set it's output to be 2 channel, which is Pro-Logic encoded. To all intents and purposes this is the same as as the optical sound track after it's been processed by the NR modules.

Posted by Michael Brown (Member # 890) on 11-27-2001, 10:32 AM:

So essentially there is no difference between analog Dolby on say VHS and analog dolby on 35mm film???

If this is the case then why do cinemas buy several thousand pound dolby processors when they could pick up a home pro logic decoder for a couple of hundred pounds?

Posted by Josh Jones (Member # 447) on 11-27-2001, 10:54 AM:

two words, Noise Reduction

Josh

Posted by Aaron Sisemore (Member # 145) on 11-27-2001, 11:57 AM:

>>So essentially there is no difference between analog Dolby on say VHS and analog dolby on 35mm film???<

Josh got it right, the two formats use different noise reduction systems: 35mm film uses A-type or SR, and VHS uses B-type (same as cassette tapes). The matrixed tracks are basically the same however, and the later version Cat 150 matrix cards use the same Pro-Logic decoder chip as many home units, but without the proper NR it is not going to decode properly.

-Aaron

Posted by Brad Miller (Member # 2) on 11-27-2001, 02:24 PM:

Actually, VHS Hi-Fi does not use any Dolby noise reduction. You're thinking of the old twin linear tracks back in the early 80's that split the single mono track (still used today) into two tracks and utilized Dolby B NR to combat hiss. To my knowledge, it's been almost 15 years since the last stereo linear VHS machines have been manufactured that used Dolby B NR.

Posted by John Walsh (Member # 168) on 11-27-2001, 03:55 PM:

Don't forget that the professional cinema processors also have 24-band EQ settings for each channel, removable PC cards, (for field servicing) both A and SR noise reduction, an optical preamp, back-up capablity, and (depending on the exact processor) other extra features a home user would probably not need.

Posted by Patrick de Groot (Member # 858) on 12-02-2001, 03:18 PM:

Well, you really don't have to own a dolby cinema processor to get good sound. I guess they just have to make money by selling them at these ridiculous prices because the professional cinema market is much smaller then the home cinema audio market...

You can get very good sound by using
-2 channel microphone pre-amp with some kind of noise reduction (threshold,..)
-pro logic decoder
-equalizer
-some good home amplifiers (which is good enough for not to big screens)

Posted by Gordon McLeod (Member # 33) on 12-02-2001, 03:33 PM:

threshold noise reduction only helps remove background noise
It does not retore the dynamic range of the track
Dolby Noise reduction both A and SR use a form of companding that is complementary ie the amount of compression going in is the amount of expansion needed going out
Unlike regular Companders (DBX and the like) they are a threshold base and multibanded and in the case of SR a few more goodies thrown in
While it works okay for a home enviroment it definitly isn't "film done right" for a paying audience
With the low cost of used DOlby 360 NR units they would work well (with 280T cards for sr) with your prologic unit. One must remember that there are varing degrees of accuracy in prologic units and in headroom.
Also a solarcell would like to see a virtual ground preamp or one with a very low impedance and most mic preamps are much higher

Posted by Patrick de Groot (Member # 858) on 12-02-2001, 03:47 PM:

It is nice that dolby A and SR are designed that they can be played on equipment which is not dedicated to this type of noise reduction. Of course you get a degraded sound quality, but it can be good enough for professional presentation if good equipment is used and tested. I really would like people to try it out just for the fun of it and listen to the sound it can produce!

Posted by Gordon McLeod (Member # 33) on 12-02-2001, 03:59 PM:

At present Dolby CP50's can be bought on ebay for $250.00 USD or less and the extra costs is to upgrade to SR
A decent Prologic unit 3 1/3octave EQ units a Stereo noise reduction unit and preamp cannot be had for that
Also with all seperate devices they are usually unbalanced in/out and that can lead to all sorts of ground problems

Posted by Pete Naples (Member # 761) on 12-02-2001, 04:38 PM:

Ayuppers!

Cinema Processors are just that, CINEMA processors, with all the features and facilities designed for professional cinema use. Domestic processors are just that, DOMESTIC!

I once made the mistake of getting involved with a cinema that was having a sound system installed with a domestic pro-logic unit at it's heart. The equipment had been sold to them by a stage equipment supply company, and when they started to have problems I got involved. First problem, the cell didn't like the pre-amps they used, two brands of pre-amps later and we got usable signal, second hassle, the surround delay on the processor wasn't long enough for the theatre (being much larger than the average sitting room), install an outboard delay unit, and we get round that one. No on board eq', so three graphis eq's were banged in. After all that it sounded, well mediocre, and between what the client had originally spent plus getting me involved, they might as well have bought the real thing in the first place. It's all now about to be replaced with an Ultra Stereo. If I ever get the chance to go down that road again I don't think I'll bother.

Posted by Gordon McLeod (Member # 33) on 12-02-2001, 05:50 PM:

There were a couple of CP100's on ebay a while back that went for a about 100.00 and in fact there is very little wrong with those still for analogue playback. Just a little more complex than some are used to

Posted by Steve Guttag (Member # 268) on 12-02-2001, 11:59 PM:

>>"I really would like
people to try it out just for the fun of it and listen to the sound it can produce!"<<

I have, several times by morons that thought it sounded pretty good...in my opinion...every time it sounded like utter crap. Only a fool would think this sort of set up is anything resembling "professional."

Pre-amps for microphones and pre-amps for projector soundheads while similar are not identical, even when both are of high quality...how many of your mic pre-amps have slit-loss correction? Mic pre-amps worked OK in the days of mono where HF response was poor (as was LF response, but I won't go there) but are totally unsuitable for the current Dolby-SR encoded films.

Then there is the noise reduction...consumer doesn't have it and most cinema equipment has poor quality versions of it. High-quality Dolby-SR is very special indeed and can make all the difference in the overall sound quality.

The pro-logic stuff can be delt with by consumer stuff but as others have pointed out, the delay on the surround channel is often inadequate. Lastly, the B-chain for consumer is often inadequate...I don't know of any consumer level stuff with either 1/3 octave EQ or 5-band parametric. Sure you can add this externally but to use good quality EQ (RANE, Klark-Technik and the like) will set one back enough to nullify any alleged cost savings with the consumer stuff.

In short, while using a genuine cinema processor for cinema sound isn't essential, it sure makes it a whole lot easier and I have yet to see anyone do it well any other way for a conventional cinema. Then there are all the other features catered to cinema like switching via automation, dealing with non-sync, multiple projectors or having one's favorite digital sound built-in.

Steve

------------------
"Old projectionists never die, they just changeover!"

Posted by System Notices (Member # 2357) on 03-28-2012, 01:58 PM:

It has been 3768 days since the last post.