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This topic comprises 2 pages: 1 2
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Author
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Topic: Using CP-50 at Home ?
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Nic Dreier
Film Handler
Posts: 13
From: Basel, Switzerland, Europe
Registered: Jan 2000
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posted 01-27-2000 02:37 PM
Hi there,first I'd like to say a big HELLO from Europe/Switzerland to all members of this great forum. It's such a big help in solving daily problems in a cinema. I work in a small chain with 3 duplex-houses and 1 single-screen house. All auditoriums are at least equipped with DTS, most also with SR-D and SDDS. One is THX approved. So this is my first post and I hope, you can help me. I'm interested, if someone has ever tried to use the good old CP-50 at home. I'd like to connect my TV, VCR or DVD Player to the CP-50 so that sound is sent trough the 2:4 Matrix. Unfortunately the Non Sync Input is not beeing processed through these cards like the newer Dolby models. I know that the line levels of DVD Players, TV out, etc. do not match to the Preamp levels of the CP-50. So I tried to fix the levels by using a Soundmixer, but the result was only poor sound quality. I've tested all the cards at the cinema and they seem to work fine, but I don't get that thing to work at home. Is there a possibility to achieve a way, that the Non Sync Input is going to be sent through the hole card-array (A-Reduction, 2:4 Matrix etc.) ??? Well, thanks in advance for your help. Greetings Nic from Switzerland
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Nic Dreier
Film Handler
Posts: 13
From: Basel, Switzerland, Europe
Registered: Jan 2000
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posted 01-28-2000 03:45 AM
So then, I think I have to upgrade the CP-50 Motherboard with a Pentium III 600 Mhz ;-)But seriousely, Is it possible to use cards of a CP-55 or CP-45 in the CP-50 ?? I mean can I mix the 200-er with the 100-er series ? I would not expect that such an array is working. Maybe I have to send it to my Dolby Tech. But that will cost me a fortune :-(. Thought there could be a possibility to do it myself. Thanks and Greetings Nic
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Stefan Scholz
Expert Film Handler
Posts: 223
From: Schoenberg, Germany
Registered: Sep 1999
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posted 01-28-2000 05:40 AM
Feed your Video equipment into the testpoint marked PREAMP OUT. This is 300 mV sensitivity, and should match with your home gear. Going through the preamp, which within most Dolby processors has never been a work of ingeniousity, will only degrade quality. Why shoul you attenuate by 30 dB, and amplify afterwards with 30 dB? Do not forget to select the Stereo with surround DOLBY OFF format, as home stereo signals not Dolby SA or Dolby SR encoded.
If you want to use a CP 50 for home purpose, be sure, that it was equipped with an SR-A5 Dolby SR adaptor. This normally warrants, that the cards have been updated to the higher dynamic range/headroom versions of later revisions. If the decoder board (CAT 150) is below "CAT 150 D" revision, forget it, they just have poor decoding.
My friend uses one, which had Dolby SR, and this works fine at home with film and video sources.
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Steve Guttag
We forgot the crackers Gromit!!!
Posts: 12814
From: Annapolis, MD
Registered: Dec 1999
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posted 01-30-2000 03:10 PM
>>"Gordon is correct in stateing that the Cat150B card or below is unsuitable, to play back Dolby SR on this card, You will need to install either a Cat150E of F card, I have seen them for sale on the web for little as $500, a worth while investment!."<<While I do not dispute that the later revisions of the Cat. 150 (particularly the D,E and F) have superior separation and noise figures, to say that the 150B is "unsuitable" for playback of "Dolby SR" is absurd. One has NO bearing on the other!! SR adds merely 3dB of level, well within the range of the Cat. 150B. Shoot, I know of premiers of films in some high profile theatres that still have Cat. 150B (simply because they haven't failed yet) and no one has run out complaining (not even from the studios). Would I recommend the upgrade, you bet and have every time I was given the chance. But that has NOTHING to do with SR...just that the later cards will decode modern prints better than the early ones even if they are only Dolby-A type. Steve ------------------
"Old projectionists never die, they just changeover!"
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Steve Guttag
We forgot the crackers Gromit!!!
Posts: 12814
From: Annapolis, MD
Registered: Dec 1999
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posted 01-30-2000 06:44 PM
>>"One must remeber that 3db of level is doubling the voltage gain and even Dolby has been very adverse to the use of the 150B with SR for that reason. The transconductance amps usually have a problem with the extra heat the higher current generates."<<Bzzzzzzz....6dB is a doubling of VOLTAGE...3dB is a doubling of POWER. Dolby always promotes the latest versions of it's equipment as the best way to do something, why wouldn't they? If their alledged concerns were true, there would be massive failures out there, when there are not...furthermore, only an foolish engineer would design something that was so close to the edge of failure (3dB) in low voltage/power situations such as the Cat. 150 which operates at either 300mV or 500mV buss levels. From what I can tell the card has ample headroom. It operates at much higher levels and the optical track is pretty heavily restricted on its maximum output. There is just 6dB above Dolby level. Steve ------------------
"Old projectionists never die, they just changeover!"
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