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Author Topic: How to get a better Dolby-A sound when playing SR-Films Patrick A. Meister Film Handler Posts: 22 From: Switzerland Registered: Aug 2003 posted 04-02-2004 11:26 AM                     Hello everyone I'm using a CP50 with A-NR in it. In my little home cinema I always play SR-Films. In the moment, SR is too expensive for me, so I'm trying to get a better Dolby-A sound outa the CP50. Is this possible, that eaven with A-NR, SR Films souund better? Patrick  |  IP: Logged Mitchell Dvoskin Phenomenal Film Handler Posts: 1869 From: West Milford, NJ, USA Registered: Jan 2001 posted 04-02-2004 02:56 PM                     This is a case of, if you can’t do it right, don’t do it at all. Dolby SR will never sound good being processed by a Dolby A decoder. At one time, Dolby made an external box that added SR to the CP50. I also believe, but not sure, that at one time there were also slot compatible cards that allowed you to remove the “A” boards and replace them with “SR” boards (losing “A” capability). If these options are not possible for you, you would do better to bypass the CP50 all together, and feed the photo cell’s left right signal into a mike mixer, to boost the volume level, and the output of the mike mixer into a consumer Dolby Pro-Logic receiver. This will give you left center right surround without any noise reduction. It is not right, but will sound better than running SR thru Dolby A.  |  IP: Logged Manny Knowles "What are these things and WHY are they BLUE???" Posts: 4247 From: Bloomington, IN, USA Registered: Feb 2002 posted 04-02-2004 03:21 PM                     If it's that important to you, why not save $$$ towards an SR capable system and, in the meantime, enjoy your CP50 the way it is. But, seriously, if your budget is limited to the point where you have to sacrifice proper SR playback then I would question the choice to mess with film. "Video done right" is cheaper and more easily attained that "film done right." Especially in a home-theatre situation. With DVDs you can enjoy Dolby Digital sound as well as easy access to thousands of movies (and TV programs). I would bet that proper storage of film prints is unlikely in a "collector" environment. Especially if there are budget concerns. Regardless, it is certainly easier and cheaper to collect, store and show DVDs.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 04-02-2004 08:07 PM                     Kep your eye on the used market for used CAT 280T's. They do come up on a fairly regular basis. I bought a pair fomr a recording studio equipment dealer in Portland, OR about 5 years ago for 400.00 U.S.. Now thats a bit on the cheap side but they can be found for a reasonable price. When running SR on a CP-50 its also best to have the later style cards such as the CAT 517 fader and one of the later decoder cards so that you don't haev to worry about signal overloading. Mark  |  IP: Logged Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 04-02-2004 09:54 PM                    Mitchell's idea is going to eliminate slit loss correction and house EQ. If SR through A is worse than no NR at all (doubtful I think, but likely varies with the film) then it would be better to put a couple of NR bypassing switches on the backplane so that the rest of the CP50 remains functional. On a 50 with the old button card you can turn off NR independent of other features but as I recall that is what causes the Academy filter to kick in. Come to think of it, it is a simple modification to add a switch to the meter card (where the filter is located) so you can turn it off so it doesn't kick in when the NR button is off. Manny's idea eliminates a film hobbyist just because he can't do everything perfectly just yet. That's something you can say about a theatre which asks paying customers to put up with an improper performance but I'm not entirely comfortable saying that to someone who just wants to have some fun with film and film equipment. Patrick, you are aware of course that SR prints are recorded at a lower average level than A-type and you'll need to bring your main fader up a little from where you run A-type prints.  |  IP: Logged Patrick A. Meister Film Handler Posts: 22 From: Switzerland Registered: Aug 2003 posted 04-03-2004 02:10 AM                     Hello My CP50 already contains this newer switch card with the format 05 SR. To play films in SR (with the A NR capability), an SRA5 must be added. If not, a link must be there to link the signal for "Pre-Amp out" to "From Surround Decoder". In a way I've got something like SR, but it is just the signal out of the Pre-Amp. Last days I tryed to get a better sound, when I turn around on the EQs...well, it was not very successful. The SR film sound with A-NR sounds eaven better than without any NR. I'm looking for a CP65 or CP45... Patrick  |  IP: Logged Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 04-03-2004 08:29 AM                    I don't doubt that A-type sounds better than no SR at all. Both processes raise the level of the quieter sounds so they don't get lost in the background noise then on playback put them back down in level to where they should be. SR does this more extremely than A and works somewhat differently. Still better to drop things back part way than not at all. In the early days of SR Dolby liked to say the processes were somewhat compatible and actually touted the fact that a non-SR equipped theatre playing an SR track via A might actually benefit since these theatres would likely be noisier than the better houses that were early adopters of SR, saying that the reduced dynamic range of SR played in A would help these quieter sounds to be heard. Not everyone agreed nor wanted compromised playback so there were dual inventories of SR and A prints just like in the early days of Dolby Stereo (A) there were dual inventories of stereo and mono tracked prints. You do not have to have the SRA5 adaptor. You can plug the 280T cards directly into the CP50 in place of the Cat.22's. The adaptor is there simply to allow pushbutton selection of A and SR. This was useful when both formats were common but nowadays with virtually all new prints being SR there is little need. Just put in the 280T's and keep the Cat.22's nearby in case you ever need them for an A film.  |  IP: Logged Patrick de Groot Expert Film Handler Posts: 161 From: Sprang-Capelle, Netherlands Registered: Apr 2001 posted 04-03-2004 09:54 AM                     quote: If these options are not possible for you, you would do better to bypass the CP50 all together, and feed the photo cell’s left right signal into a mike mixer... Don't do that, in that case you have no noise reduction at all... I thought Dolby SR NR was made so that is was still possible to run it with Dolby A NR. It sure sounds better with then without it! BTW you can still use the stereo matrix of the CP applied to external sources by using the non-sync 2:4 decoding...  |  IP: Logged Scott Norwood Film God Posts: 8146 From: Boston, MA. USA (1774.21 miles northeast of Dallas) Registered: Jun 99 posted 04-03-2004 10:21 AM                        The CP-50 doesn't do matrix decoding of non-sync in its default configuration. There's some way to modify it to do this, but it doesn't come that way out of the box.  |  IP: Logged Patrick A. Meister Film Handler Posts: 22 From: Switzerland Registered: Aug 2003 posted 04-03-2004 12:46 PM                     WEll, does someone know, HOW the CP is programmed? The CP55 and CP200 etc use Diodes on Cards for programming the formats...how does this work in the CP50? I just see some ICs on the Control-Card  |  IP: Logged Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 04-03-2004 06:35 PM                    What programming? The button card is telling the NR to be on or off, the Academy filter to be on or off, and the matrix decoder to do 2:4 decoding OR sum Lt/Rt into C for mono. More amazing facts about the CP50: The NR cards (Cat.22 or Cat.280T each contains a line drive amplifier. In recording studio equipment the signal coming from the NR circuitry is typically sent right back to the card to the line amp before leaving the card a 2nd time and exiting the equipment. On the CP50 these amplifiers are not used by the signal enroute from NR to meter/filter cards but are used by the final L and R signals after EQ and fader. The output card contains line amps for C and S only. L and R get sent back up the backplane to the NR cards' line amps before finally emerging at the output terminals. Useful to know this when diagnosing problems or modifying the units. The original Cat.64 EQ cards contain a circuit called "head equalizer" which is unrelated to the card's primary function and not used AFAIK by any CP model. This circuit provided HF gain adjustment akin to that found on a CP's pre-amp, sometimes called slit loss correction, and was used in the early Dolby Mono implementations. Send the signal to the Model E2 (1U high box containing a single Cat.64) for slit loss correction, then to the Model 364 (1U high box containing a single Cat.22 NR card) then back to the E2 for the EQ functions of the Cat.64.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 04-03-2004 09:10 PM                     Formats on the cp50 are created with a xazcto knife (to cut traces) some buss wire and solder  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 04-03-2004 11:16 PM                     Steve, In mentioning I.C.s I think he has either an old 113 or newer 113C automation card. Not too many of the old button cards are in use at least in my service areas.... Mark  |  IP: Logged Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 04-03-2004 11:24 PM                    Yes, I know. It still has buttons and it still commands the other cards as described albeit not individually like the old controls did.  |  IP: Logged Patrick A. Meister Film Handler Posts: 22 From: Switzerland Registered: Aug 2003 posted 04-04-2004 03:44 AM                     Well Steve, that's very interesting! The Line Drivers put the signal up to 1V, or 100mV if the switch is in that postion)? I already thinked of using my CP50, when I could get a CP65, as a A NR Unit for Tape Recordings! The Cat22's are able to encode the incoming signal and with the line amps there should be not a problem. But, the signal into the Cat22's has to be at Dolby Level (if playing the Dolby Level). How could I get it down to Dolby Level? Puttin' a pot in fornt of it? Another question: Is it possible to get more Volts out of the "To Power amps" connectors than only 1V? The volumeknob at Homedecoder is almost at 100%! PS: Yes, I have the 113C Card, and I cant find anything, where this card says to the components, what to do...are there some diodes or cables? Kind Regards Patrick  |  IP: Logged

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