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Author Topic: Optical Sound Marin Zorica Jedi Master Film Handler Posts: 671 From: Biograd na Moru, Croatia Registered: May 2003 posted 02-24-2004 05:29 AM                     Hallo!! From my long time in cinema i was working about optical sound and my idea is to make my own cinema sound system with Left, Right, Center and Surround outputs. First thing for that is stereo optical reader on projector. I know for solar cells, revers scan, red led readers and others, but my idea is not to buy from someone kit and upgrade cinema, idea is to make my own system!. I look a lots of manual of cinema procesor, amplifiers, readers etc. I starded to put photodiodes instead solar cell (is someone have other alternatives for solar cell), becose solar cells are much expensive, leave exciter lamp and so in projector reader. next thing is preamplifier (i've buil at cople and some are sounding vell!!!), and SR decoder (Noise Reduction Module is also but not likely becose is complicated) this is electronic part and i'we seen some procesors what have quality sound (they are without Noise reduction!!) and they not complicated at all!, after that we come to power amplifiers and speakers which are not thngs for worrying about becose everyone today can built own sperker or amplifier. Is someone interested in this, or allready working with stuff like this, if you are or you know any knowledge about this (or schematic, manual, etc.) tell me to help me with this. I know i'm very entusiastic but i think thing like this is not very complicated!!! thanks everyone for reply on this!!!!!!!  |  IP: Logged Gilbert Travin Expert Film Handler Posts: 101 From: Villeurbanne / France Registered: Jan 2004 posted 02-24-2004 07:03 AM                        Hi ! Yes, you can install DIY stereo sound pick-up instead of mono equipment ! You must use 2 solar cells pasted on a support (as low cost Siemens BPY 11 P or equivalent), photodiodes are too big : the beam must not be separated when it reaches the cells ! If you can't buy an "old" cp 50, you can use operational amplifiers (as low cost TLO 71, low noise) as preamp unit. For 4-channel decoding the best is to buy a home cinema amplifier with Pro-Logic capability. It is an artisanal realization which requires a little work and some knowledge in electronics. Operation is satisfactory if one is not too demanding !  |  IP: Logged Marin Zorica Jedi Master Film Handler Posts: 671 From: Biograd na Moru, Croatia Registered: May 2003 posted 02-24-2004 07:42 AM                     Thanks for replay, when i read you're replay i look for BPY 11 P, but i can find that component are you got any link when i can buy or saw picture of that component, another question is what you wrote to me, what is DIY stereo pick-up, and TL 07X is goog OP-IC, but do you have any schematic for preamplifier??, the thing about buying a home theatre system for decoding is good, and i already thinking about that but the problem is that are no receiver with strong power amps for large cinema, and to buy a receiver and put amps are bit expensive, if is not hard is there some schematic about SR decoder?? Thaks  |  IP: Logged Gilbert Travin Expert Film Handler Posts: 101 From: Villeurbanne / France Registered: Jan 2004 posted 02-24-2004 08:32 AM                        OK ! DIY = do it yourself, that is that you want to do ! Siemens made photovoltaic cells ; I have an old datasheet (1983) : the dimensions are 2 x 4.8 mm ; I beleave that these cells still exist : http://www.hinkel-elektronik.de/shop/430.html but I don't find the web site of the manufacturer ... I have not a specific schematic for preamplifier with TLO 71 : you can use any general purpose schematic described in an electronics book for engineers. I know that, in my school, students had realized this stereo reading (before buying a cp 50) : it worked nice with 4-channels decoding (but without dolby decoding) ! If you find a home cinema preamplifier, you can connect it to cinema power amplifiers for 4-channel decoding. (these HC preamplifiers exist, but are often more expansive than HC amplifiers) Decoding A or SR is another problem : special electronics circuits have been developed by Dolby , you can't find them in the trade ! I think that a student or a teacher in an electronics engineers school can help you to realize your system ...  |  IP: Logged Scott Norwood Film God Posts: 8146 From: Boston, MA. USA (1774.21 miles northeast of Dallas) Registered: Jun 99 posted 02-24-2004 10:15 AM                        My understanding is that the A-type patent has expired, but the SR patent is still in effect. Don't forget that there will need to be a way to switch between mono (Acadmey curve), A-type, and SR-type NR. There's also a need to be able to monitor and adjust input levels (to set Dolby level) and perform silent changeover from one set of inputs to another (unless this is a single-machine-only design). Not sure about patent issues with the matrix decoder (maybe someone else knows). I suppose that it's an interesting project, but probably not cost effective, considering how many perfectly good CP-50s and -55s are available relatively inexpensively.  |  IP: Logged Edward Jurich Master Film Handler Posts: 305 From: Las Vegas USA Registered: Jul 2003 posted 02-24-2004 11:10 AM                     FYI, I used photo-transistors ($2.00 each) on my Holmes for stereo pickup and they sound great. They need to be biased properly and you need to use photo-transistors that have 3 leads like a convential transistor.  |  IP: Logged Edward Jurich Master Film Handler Posts: 305 From: Las Vegas USA Registered: Jul 2003 posted 02-24-2004 11:10 AM                     STUPID COMPUTER CAUSED DOUBLE POST FYI, I used photo-transistors ($2.00 each) on my Holmes for stereo pickup and they sound great. They need to be biased properly and you need to use photo-transistors that have 3 leads like a convential transistor.  |  IP: Logged Marin Zorica Jedi Master Film Handler Posts: 671 From: Biograd na Moru, Croatia Registered: May 2003 posted 02-24-2004 11:11 AM                     Gilbert thanks alot for replay's, i be glad if you can emaio me that datasheet of bpy 11 is you're be ale to. i don't know are you know for BPW 34 silicium photodiode, that photodiode i was using to get stereo from film, and instaled in two working cinemas till now with my preamps, also i got an old ernemann IV projector which i used for testing. Also i know i bodering you but can you explain me a difrence betwen solar cells and other readers, what cells are so expensive and so used?? Thanks for replay  |  IP: Logged Gilbert Travin Expert Film Handler Posts: 101 From: Villeurbanne / France Registered: Jan 2004 posted 02-25-2004 04:40 AM                        Hi all Of course, the system "very low cost" I described has not a built-in academy filter for mono : the sound is nice only if the film soundtrack is good ! However, any electronician can realize such a filter with an operationnal amplifier and one or two resistors and capacitors. Yes, it is possible to find a low cost cp 50 in France (< $300), but in Croatia ??? You can try to contact Strong Europe in Villeurbanne ; they speak english http://www.strong-europe.com/ I don't know the photodiode BPW34. The difference between a photodiode and a photovoltaic cell : the photodiode (and also phototransistor) needs to be DC-biased , not the photovoltaic cell that works like a battery ! The photovoltaic cell must be loaded by a low impedance to obtain a linear response. In a cp 50 that is realised by the little transformers before the transistorised preamp. Low cost solution : you can connect the photovoltaic cell directly to a microphone input with a 1 kilohm load-resistor. Edward, can you tell us, please, the dimension of your phototransistor ? Thanks . I try to scan the datasheet of bpy 11 P.  |  IP: Logged Edward Jurich Master Film Handler Posts: 305 From: Las Vegas USA Registered: Jul 2003 posted 02-25-2004 11:12 AM                     Links to a page showing my Holmes photo-transistor pickup http://www.angelfire.com/film/shutterblade/holmes/preamp.html http://www.angelfire.com/film/shutterblade/holmes/pickup.html In my Holmes, the scan beam perfectly fits the footprint of the photo-transistors. I have seen another Holmes that this would not work because of scan beam spread. I suspect the fact that I changed to a BAK exciter lamp may have given me a better scan beam for my pickup. Link to the complete Holmes page. http://www.angelfire.com/film/shutterblade/holmes/holmes.html  |  IP: Logged Steve Kraus Film God Posts: 4094 From: Chicago, IL, USA Registered: May 2000 posted 02-25-2004 09:22 PM                    With all the reverse scan being installed doesn't anyone have a stereo solar cell you can send this fellow? While you're at it send him that dusty old CP50, too. It'll be your good deed for the day.  |  IP: Logged William Hooper Phenomenal Film Handler Posts: 1879 From: Mobile, AL USA Registered: Jun 99 posted 02-26-2004 01:01 AM                        If you're so hardcore roll-your-own, the schematics of most of the Dolby CP's are in the manuals section. Or you could start easier & primitive & stereo with the RGM MSS4000 Or, for the tube-type mono Academy purist, the Mellophone !  |  IP: Logged Gilbert Travin Expert Film Handler Posts: 101 From: Villeurbanne / France Registered: Jan 2004 posted 02-26-2004 02:44 AM                        Hi all ! Thanks for your replies ! I hope that Marin can now find a lot of solutions for his problem. Just a question to Edward : if I have correctly understood, the gap between the two phototransistors is not a disadvantage. To which distance from film they are placed ? What is the model of projector ?  |  IP: Logged Michael Schaffer "Where is the Boardwalk Hotel?" Posts: 4143 From: Boston, MA Registered: Apr 2002 posted 02-26-2004 05:59 AM                        Steve - yes, I have quite a few solar cells lying around now that I replaced many of them with red LED readers. But I would like Marin to show a little more initiative, I hooked him up with some really good contacts in Berlin, which is far closer to his location than San Diego "America`s finest city". And no, I would never give any of the CP50s away that we still have - they are living movie theater history. Marin - did you contact those people that I pointed you to in Berlin? That might be the easiest solution to your problems.  |  IP: Logged Edward Jurich Master Film Handler Posts: 305 From: Las Vegas USA Registered: Jul 2003 posted 02-26-2004 06:08 AM                     It's a Holmes Model 8. The photo-transistors are about 3/4" from the sound gate. The scan beam has a slow spread and retains the slit shape at that distance so for me it worked out well.  |  IP: Logged

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