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Author Topic: Need info on Jaxlight and sound Dovilis Paliukas Film Handler Posts: 5 From: Vilnius, Lithuania Registered: Mar 2014 posted 06-26-2014 03:08 PM                        Hello, I am new here. Thanks for granting me access here. This forum is No.1 on cinema equipment. I own couple of projectors. Now I started on Vic5 at home. I really like film. So everything is quite in working condition, had to restor platter system, fix electronics and so on. Vic5 is in nice shape and there were nothing much to fix. Today I connected sound to the power-amp that is comming from Jaxlight line amp XLA650. I do not have Dolby processor yet. But I have two mixers, amps and so on. The sound from the jaxlight comes very distorted. The jumper settings are without +6db boost and without high freq boost. It seems like it does not really amplifies it, just a bit. Maybe someone can tell me why jaxlight is used? BTW it came with victoria inside. Thanks a lot. Dov  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 06-27-2014 09:58 AM                     The jax light was one form of retrofitting projectors to red light for cyan tracks the little booster line amp was to raise the signal level of the cell back to the level that the cell normally produced with white light. That said it is fussy that you have accurate soundhead alignement and grounding also is you mic preamp a low impedance input?  |  IP: Logged Dave Macaulay Film God Posts: 2321 From: Toronto, Canada Registered: Apr 2001 posted 06-27-2014 10:14 AM                     The Jaxlight preamp only amplifies the cell output up the what you may have had with a tungsten exciter lamp, and expects to be feeding a cinema solar cell input. Going direct to a mixer is abnormal so problems can be expected. Output level is very very dependent on optical alignment and the Vic5 sound reader is prone to misalignment if there's a threading mistake or film crash. The Jaxlight is a ... hmmm... piece of crap(?) that had one advantage over full LED reader conversions - it was the cheapest way to get a system compatible with cyan sound tracks. Prone to noise and distortion and very picky about system grounding, we actively discouraged their use - not because the profit was less, just to avoid endless complaints.  |  IP: Logged Ed Inman Expert Film Handler Posts: 103 From: Jackson, Mississippi USA Registered: Jul 2004 posted 06-27-2014 02:31 PM                        You can get a Dolby CP55 for about $150 on ebay. Mine works OK with the Jaxlight preamp. I never had very good results with the Jaxlight before getting the processor. I don't have any cyan soundtracks, so most of the time I stick with a regular exciter lamp anyway. But occasionally I've found the red LED helpful in reducing noise on problem soundtracks (i.e ones that were poorly made, damaged or are otherwise excessively noisy when using white light). I have one film in particular that sounds like a freight train is rumbling in the background with white light but plays almost perfectly with the Jaxlight. Not sure why.  |  IP: Logged Mitchell Dvoskin Phenomenal Film Handler Posts: 1869 From: West Milford, NJ, USA Registered: Jan 2001 posted 06-27-2014 04:25 PM                     > sounds like a freight train is rumbling in the background with white light but plays almost perfectly with the Jaxlight. Not sure why. The lab did not do the silver retention bath, so the infrared from the white light passes thru the track. The red reader eliminates the infrared at the light source.  |  IP: Logged Dovilis Paliukas Film Handler Posts: 5 From: Vilnius, Lithuania Registered: Mar 2014 posted 06-27-2014 04:26 PM                        Thank you all for reply. First I thought that it was a regular amp. There is red light beam on sound head. So maybe i should not use jaxlight. Alighnment as i check is good. When there is less sound comming from jaxlight it sound nice, but when the input from film increases there comes the distortions of sound. Good only for background sound . Grounding is good too. I fixed that before. Will try to run it without jaxlight and will let you know. I have in a list of getting sound processor, but not at the moment. I still need to get lenses and other stuff... Thanks again.  |  IP: Logged Dave Macaulay Film God Posts: 2321 From: Toronto, Canada Registered: Apr 2001 posted 06-28-2014 09:21 AM                     The Jaxlight is actually the red light in the soundhead. The preamp is required because the signal from the solar cell - designed for a tungsten exciter lamp - is rather low with the red LED Jaxlight. There are other red light conversions that also replace the solar cell with a light sensor assembly better suited to red LED light and an integral preamp. The LED used is a line array of small LED to produce a bright line of light across the sound track. They use a linear CCD sensor: The soundtrack image is focused on the CCD array which, since it's a narrow line, needs no slit in the optics. Basically you're fighting physics with the Jaxlight: never a really good plan. There's less light available from the red LED, that light is not in the most sensitive region of the silicon solar cell pickup, the LED light is focused to a circle and passed through a slit so ~99% of the available Jaxlight light is wasted, the resulting low output signal then goes through cable with questionable (if any) shielding to a high gain preamp hopefully located close by. There have been hundreds (thousands?) of Vic5 projectors with good LED soundhead readers - BACP, Component Engineering, Kelmar, and others made good ones - that were scrapped or are sitting idle in now-digital booths. Surely you can get a decent reader cheap and use it instead of the Jaxlight. The cinema industry switched to red LED sound readers because the soundtrack printing process was changed to eliminate a lot of extra steps in print production, eliminate the use of silver (expensive), and reduce the production of hazardous waste. The silver tracks blocked infrared light, and the tungsten exciter lamps system with a silicon solar cell worked on a broad light spectrum including infrared delivering quite decent signal level and good fidelity through a narrow slit in the sound lens - there was so much light energy in the exciter lamp beam that using a fraction of it through the slit was practical. The new cyan silverless soundtrack image did not block infrared. With a white tungsten lamp, the infrared passing through the entire track width produces a lot of noise just from the random variations in the film density. The actual desired soundtrack signal level is also reduced by about 10dB. That adds up to a low volume noisy soundtrack. The cyan light blue soundtrack does block a high percentage of red LED light. A full reverse scan red LED conversion cost in the $1000.00 range plus a fairly tedious installation. The Jaxlight was, I think, around $300.00 and installation was much simpler: you just took out the exciter lamp, plugged in the Jaxlight, wired in the preamp, and set the processor levels.  |  IP: Logged Dovilis Paliukas Film Handler Posts: 5 From: Vilnius, Lithuania Registered: Mar 2014 posted 06-28-2014 10:47 AM                        Thanks again for explanation. From photography and filters I know that when it comes CYAN and RED it becomes near black. So cyan soundtrack becomes more contrasty to read. When tungsten is used I think it becomes very low in contrast so noise raises and sound level goes down. When I used Meopta XS5, I did my own modification with RED led because of cyan soundtrack, and not changed reader or added any preams before mixer. It worked quite nice, but I blew all high freq tweeters. Haven't tried to find out why.... The high frequency was not boosted at all. So now VIc5 has jaxlight with preams and there is a lot of distortion of sound itself. It is not ground problem, or noise level problem. It is that the sound from jaxlight becomes distorted itself when sound level from soundtrack becomes higher... Correct me if I am wrong. cheers  |  IP: Logged Dave Macaulay Film God Posts: 2321 From: Toronto, Canada Registered: Apr 2001 posted 06-28-2014 12:12 PM                     If you're feeding a low impedance mic input, the preamp may be overloaded and distorting on higher level sound. The Jaxlight wasn't really prone to distortion - it had problems with noise mostly.  |  IP: Logged

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