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» Film-Tech Forum   » Operations   » Film Handlers' Forum   » FP20 Dolby Digital Analogue Output (Page 1)

 
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Author Topic: FP20 Dolby Digital Analogue Output
Steve McAndrew
Film Handler

Posts: 84
From: Hemel Hempstead, Herts, UK
Registered: May 2015


 - posted 02-02-2016 04:24 AM      Profile for Steve McAndrew   Email Steve McAndrew   Send New Private Message       Edit/Delete Post 
I have a Kinoton FP20 that has a Dolby Digital Reader installed. The projector has two XLR sockets that are connected to the reader. If I connect an amplifier to these sockets I get sound but it is quiet, even with the amplifier at full volume. Connecting to the Line In of a mixing desk I get louder sound but quality isn't great (buzzing etc). Connecting to the Mic level on a mixing desk doesn't really work.

Should the outputs be grounded to the earth of the projector in some way?

Does anyone have any tips to obtain decent sound?

Thanks in advance.

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Dave Macaulay
Film God

Posts: 2038
From: Toronto, Canada
Registered: Apr 2001


 - posted 02-02-2016 06:39 AM      Profile for Dave Macaulay   Email Dave Macaulay   Send New Private Message       Edit/Delete Post 
I don't think that what you have there is Dolby Digital. You need an outboard processor to decode the digital signal. If there is a reader unit labelled with the double-D and "Dolby Digital" there's likely nothing connected to it, it uses a pretty fat multi conductor cable directly to the decoder.
It seems like possibly you're getting the signal from a bare "solar cell" analog sound reader but that would be odd if there's a digital reader, usually a reverse scan optical pickup would be included (these tend to have pre-amps built in). These "solar cells" are technically current sources, and don't play nice with most amp or mixer inputs.
If it is a stereo solar cell signal, just add a load resistor across the outputs and connect to your amp. Try around 2K, it's been a long time since I did this and don't recall the optimum value.
Even reverse scan readers with pre-amps have relatively low signal strength but should be fairly good on a mic input. Sound quality is not excellent without Dolby decoding: film tracks were mostly Dolby SR in the last few decades but a Dolby A decoder is better than nothing.
The light source directly affects signal volume and affects quality as well. If it has a red LED the alignment is critical, these are easy to knock out of adjustment which gives you very low level, and can give weird distortion as well.

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Steve McAndrew
Film Handler

Posts: 84
From: Hemel Hempstead, Herts, UK
Registered: May 2015


 - posted 02-02-2016 07:40 AM      Profile for Steve McAndrew   Email Steve McAndrew   Send New Private Message       Edit/Delete Post 
Thanks for the reply.

The reader is the original one that was supplied with the Kinoton, it is Dolby Digital, but at the moment has nothing connected to those terminals. It has 2 Red Lasers, one for Dolby Digital and one for analogue, which is the connection I am using.

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Sam D. Chavez
Film God

Posts: 2053
From: Martinez, CA USA
Registered: Aug 2003


 - posted 02-02-2016 09:59 AM      Profile for Sam D. Chavez   Author's Homepage     Send New Private Message       Edit/Delete Post 
I take it the LEDs are Lighted? Not lasers I think..

I believe the power for the analog readers comes from the Dolby Digital cable connected to a DA20/CP500/CP650. No cable, no power.

Send a picture of the soundhead so we can tell what you have.

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Steve McAndrew
Film Handler

Posts: 84
From: Hemel Hempstead, Herts, UK
Registered: May 2015


 - posted 02-02-2016 10:25 AM      Profile for Steve McAndrew   Email Steve McAndrew   Send New Private Message       Edit/Delete Post 
Everything on the reader is working, I am getting sound, it's just not very loud. I will try to attach a picture.

Thanks for your help.

 -

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Sam D. Chavez
Film God

Posts: 2053
From: Martinez, CA USA
Registered: Aug 2003


 - posted 02-02-2016 11:04 AM      Profile for Sam D. Chavez   Author's Homepage     Send New Private Message       Edit/Delete Post 
The LEDs do fade a lot over the years. The analog one may also have been bumped and if it's even slightly out of position vertically you can lose the output level by 10dB or more. You can try rotating the LED brackets a bit with something like Dolby Tone running and you'll hear it going up and down in level. There is definitely a sweet spot.

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 11991
From: Annapolis, MD
Registered: Dec 1999


 - posted 02-02-2016 11:33 AM      Profile for Steve Guttag   Email Steve Guttag   Send New Private Message       Edit/Delete Post 
Kinoton powers its own LEDs/preamps...the sound processor only has to deal with the CCD for digital or optical preamp for analog.

But I think the pros here are likely overlooking one key bit of equipment that is normally a "given." What is your cinema processor? That is, what is the optical preamplifier that you are using?

The OP said they are using the LINE IN of a mixing "desk".

The outputs from the soundhead are at "mic" level (closest approximate level). Luckily, there shouldn't be any DC shift in the level and you definitely DON'T want any Phantom supply in there.

You should also be aware that the output presumes not only a proper optical preamp, preferably with slit loss correction, but also most movies will have a form of noise reduction on them (Dolby A or Dolby SR) so the quality of sound will be wanting by just using mic input.

It would be advisable to pick up a used cinema processor (anybody's though you can probably get a good one for cheap right now, if it hasn't been thrown away) and then feed that into your sound system, either via mixer or straight).

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Jonathan Wood
Expert Film Handler

Posts: 191
From: Oxfordshire, United kingdom
Registered: Jan 2008


 - posted 02-11-2016 05:30 PM      Profile for Jonathan Wood   Email Jonathan Wood   Send New Private Message       Edit/Delete Post 
Hi Steve
As others have said , your problem is your not using a proper CP. If you can get hold of one then you'll need to make up a new analogue cable using a molex 6 pin plug and suitable cable (belden 8723) . How u connect to the cp will depend on the model, I have a cp500 which needs a DB9 connecter , I also have a cp55 which just needs bare wires which u solder . I have the pin out for that board if you need it, the cables easy to make. If you want to stick with using a pa amp then you will need to ground the analogue board to the chassis of the amp to stop the buzz. You do this by connecting either pin 2 or 5 (from memory ) on the 6 pin connector on the analogue board, to a suitable ground on the amp (the belden cable has a drain wire for just this purpose ) This all worked fine for me when I set up an FP40 and a Vic 5 . A proper CP will make a huge difference to your sound . Good luck.

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 11991
From: Annapolis, MD
Registered: Dec 1999


 - posted 02-11-2016 05:52 PM      Profile for Steve Guttag   Email Steve Guttag   Send New Private Message       Edit/Delete Post 
Note again...the OP said it had an XLR type connector...this would be typical for a Kinoton retrofit. The presumption is it was an FP20 with an XLR from the factory so all one would have to do is feed the connector through the chassis and screw down the new connector.

This is the kit it would have originally come with and presuming the tech used the kit as is on the conversion...he just needed a suitable 5-pin XLR/cable and mic level preamps.

 -

Kinoton's color scheme was:

- sound output left - (yellow)
- sound output left + (brown)
- sound output right - (white)
- sound output right + (green)

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Steve McAndrew
Film Handler

Posts: 84
From: Hemel Hempstead, Herts, UK
Registered: May 2015


 - posted 02-13-2016 03:27 AM      Profile for Steve McAndrew   Email Steve McAndrew   Send New Private Message       Edit/Delete Post 
Many thanks for all the replies.

I managed to get hold of a CP45 but the sound was awful, I actually suspect the unit might be faulty.

I have managed to get decent sound though, the addition of a DI box with PAD settings has given me some control over input levels and I now can get very acceptable sound without any buzz.

I have also sourced a CP55 which I will experiment with when I receive it.

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Jonathan Wood
Expert Film Handler

Posts: 191
From: Oxfordshire, United kingdom
Registered: Jan 2008


 - posted 02-13-2016 05:53 AM      Profile for Jonathan Wood   Email Jonathan Wood   Send New Private Message       Edit/Delete Post 
Hi Steve
The cp45 might have been in bi amp mode ( not sure if this CP had this feature , I'm sure someone on here wiser than me here can confirm,) resulting in very muffled and distorted sound when using a non bi amp set up. . Have a look at the manual and see if it can be set for bi amp if so its prob just a case of changing some jumpers on the board to get it to work with your amp set up. I found this with a cp500 and after pulling the jumpers out it sounded fine .

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Dave Macaulay
Film God

Posts: 2038
From: Toronto, Canada
Registered: Apr 2001


 - posted 02-13-2016 09:28 AM      Profile for Dave Macaulay   Email Dave Macaulay   Send New Private Message       Edit/Delete Post 
Yes, the CP45 has internal bi-amp crossovers. They are activated on the CAT510 board: switches 4, 5, 6 ON for LF/HF crossover, OFF for full range output. (L, C, R respectively)
This was Dolby's "budget" processor and cuts a few corners, but it should sound fine.
With a CP55 you can use a CAT222SR/A DSP card for Dolby decoding - the same card used in the CP45... and generally considered not too good. You could also find an SRA5 outboard SR adapter, using CAT350T SR cards in it and the original CAT222 Dolby A cards in the CP55. These are very complicated analog cards, and considered the best. The SRA5 and CAT350T cards were $$$$ not long ago... but you should be able to find them pretty cheap now.
If you can find a used CP65, it's considered by many to be the best Dolby film processor. You can use the 222SR/A... or install CAT222 and CAT350T cards in the chassis for ideal Dolby A and SR decoding.
You need some alignment test films (Dolby level and pink noise definitely, there are others not as vital) to set up the soundhead regardless of what processor you have. These can be hard to find now. Dolby encoded optical tracks (basically every track in the last several decades) will sound "off" with no decoder or incorrect level.

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16061
From: Bountiful, Utah
Registered: Jun 99


 - posted 02-13-2016 05:16 PM      Profile for Mark Gulbrandsen   Email Mark Gulbrandsen   Send New Private Message       Edit/Delete Post 
I had to change out the LED's in my PK-60 before I could even use it. IDK how they were using it at the theater it used to be installed in....

Anyhow, the Kinoton LED's are not meant to be replaced individually in the field. Kinoton would rather soak you lots of $$$$$$$ for the replacement part already installed and aligned on the mount. However, It can be done in the field... it's just not very easy to do. Also, check the piece of foam that's inside the Dolby Digital CCD camera. My foam had deterioated and I had to clean out the pieces of crud from it and make a new foam mask.

Mark

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 11991
From: Annapolis, MD
Registered: Dec 1999


 - posted 02-13-2016 06:09 PM      Profile for Steve Guttag   Email Steve Guttag   Send New Private Message       Edit/Delete Post 
For the record...I always changed the Kinoton LEDs individually, never via the uber expensive bracket with the LED. It is just slightly difficult since you are soldering in mid-air but the "heat shrink" they use is way cool...slide it back out of the way do your work, slide it back over the connection...all done.

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System Notices
Forum Watchdog / Soup Nazi

Posts: 215

Registered: Apr 2004


 - posted 11-03-2017 01:21 AM      Profile for System Notices         Edit/Delete Post 

It has been 628 days since the last post.


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