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» Film-Tech Forum ARCHIVE   » Operations   » Film Handlers' Forum   » EQ'ing a CP50 (Page 1)

 
This topic comprises 2 pages: 1  2   
Author Topic: EQ'ing a CP50
Geof Abruzzi
Film Handler

Posts: 14
From: Mesilla, NM, USA
Registered: Jun 2002

- posted 11-12-2002 04:49 PM      Profile for Geof Abruzzi   Email Geof Abruzzi   Send New Private Message       Edit/Delete Post 
I have several questions concerning our Dolby CP50. We are installng new speakers in our theater, and I want to re-EQ once they're in. Unfortunately we haven't got a pink noise card, and we don't have an extender either (to be able to adjust the EQ's with them out of the box.) The only prices for these items I've found are higher than our non-profit will currently allow ($350+ each).
My easier question would be if anyone knows a good souce for things like these used (and cheaper). Alternatively, I have an RTA with a built in signal generator. Is it possible to use this rather than the card? If so, should I bring it in through one of the projector inputs, or somewhere else? Any info on this would help greatly.

Geof

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

- posted 11-12-2002 04:54 PM      Profile for Gordon McLeod   Email Gordon McLeod   Send New Private Message       Edit/Delete Post 
The Cp50 varries in the backplane design If it has the daughter board on the back then yes an external pinknoise source can be injected for the lcr channels but not the sub

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Aaron Sisemore
Flaming Ribs beat Reeses Peanut Butter Cups any day!

Posts: 3061
From: Rockwall TX USA
Registered: Sep 1999

- posted 11-12-2002 07:10 PM      Profile for Aaron Sisemore   Email Aaron Sisemore   Send New Private Message       Edit/Delete Post 
Unfortunately, however you are basically screwed unless you have the extender cable adaptor, otherwise an EQ job will take many many many hours of unplugging the Cat 64, making a tweek, plugging the 64 back in, looking at the RTA, unplugging the 64, making another tweek, plugging the 64 back in, etc etc etc...

Bringing the pink noise thru the projector input would not be recommended as it has to pass thru the NR and signal processing stages, and will be impossible to isolate individual channels as you can with the cat. 85C.

See if you can locate a technician's services to get the EQ done properly. It will likely cost less than the components you require to do it yourself.

-Aaron

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Steve Kraus
Film God

Posts: 4094
From: Chicago, IL, USA
Registered: May 2000

- posted 11-13-2002 01:35 AM      Profile for Steve Kraus     Send New Private Message       Edit/Delete Post 
It's not that difficult to inject a signal into the middle of the CP50.

Do you have a Cat.160 subwoofer card or is that slot filled with a blank (except for some traces) card called a 110L? (That's even assuming you have a Cat.150 2:4 channel decoder and not the old 110 & 116.)

If you are set up with no subwoofer card and the link card, the link card jumpers Left-Total and Right-Total across that gap. BUT, to use the Cat.85C pink noise generator you'd plug it into the 110 slot and the link card then gets reversed (note the edge connectors on both ends) and plugged in in place of the Cat.150 to jumper L,C,R,S across the gap where the 150 decoder was. So for starters, you might consider tack soldering a connection right on the "150" end of the 110L link card:

L is on the contact 10 - contact 4 connection, C is 8/5, R is 7/6 and S is 2/1. Inject your signal there. An alternative is to tack onto 1,4, 5 and 6 of the 150 connector on the backplane.

As for extenders, you can live without it although it's awkward. You ought to be able to reach into the CP to adjust the pots "live" on the R and possibly on C with the card in place and the neighbors to the left out, depending on the size of your hand. In fact, with the 150 and 110L out (hooking onto the backplane) you can probably adjust L as well.

I think the meter card can come out for this but the Cat.22's must remain in because Dolby availed itself of a line drive amp found on each Cat.22 card (those cards are also used in recording studio gear) and thus the Cat.117 fader/output card contains line drive amps only for C and S while L and R get sent back to the Cat.22's on board amps and then to the output terminals.

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Geof Abruzzi
Film Handler

Posts: 14
From: Mesilla, NM, USA
Registered: Jun 2002

- posted 11-14-2002 09:13 AM      Profile for Geof Abruzzi   Email Geof Abruzzi   Send New Private Message       Edit/Delete Post 
Thanks, this is is the information I need. It looks like I can tap into the backplane from the back of the unit since all the pins for mounting the connector are visible from there. I was also wondering what level the signal should be at?

On a related not, does anyone know a tech in southern New Mexico, or El Paso?

thanks.

Geof

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Antonio Marcheselli
Phenomenal Film Handler

Posts: 1260
From: Florence, Italy
Registered: Mar 2000

- posted 11-18-2002 05:03 AM      Profile for Antonio Marcheselli   Author's Homepage   Email Antonio Marcheselli   Send New Private Message       Edit/Delete Post 
What about equalizing a CP65 without a pink noise card? Is it possibile to feed pink noise into each channel?

Bye

Antonio

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Pete Naples
Phenomenal Film Handler

Posts: 1565
From: Dunfermline, Scotland
Registered: Feb 2001

- posted 11-18-2002 05:14 AM      Profile for Pete Naples   Email Pete Naples   Send New Private Message       Edit/Delete Post 
Antonio,

Yes, one could inject pink noise via the 6 channel input intended for use with a Dolby Digital processor (DA20). I don't know what the correct level is off hand though.

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Antonio Marcheselli
Phenomenal Film Handler

Posts: 1260
From: Florence, Italy
Registered: Mar 2000

- posted 11-18-2002 05:33 AM      Profile for Antonio Marcheselli   Author's Homepage   Email Antonio Marcheselli   Send New Private Message       Edit/Delete Post 
Great!
I really don't know much of CP65: does it have a 6ch input by default? I would like to help a friend of mine that manage a small theater outside the town that actually cannot afford a tech for equalization. He told me that the sound is very poor and I would like to help him. Can anyone help me about the input level?

Antonio

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Pete Naples
Phenomenal Film Handler

Posts: 1565
From: Dunfermline, Scotland
Registered: Feb 2001

- posted 11-18-2002 06:13 PM      Profile for Pete Naples   Email Pete Naples   Send New Private Message       Edit/Delete Post 
All CP65 have a six channel input. However it won't work fully unless there's a Cat443 installed. Lack of Cat443 wouldn't prevent you from injecting pink noise though, assuming the right level!

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Antonio Marcheselli
Phenomenal Film Handler

Posts: 1260
From: Florence, Italy
Registered: Mar 2000

- posted 11-18-2002 07:31 PM      Profile for Antonio Marcheselli   Author's Homepage   Email Antonio Marcheselli   Send New Private Message       Edit/Delete Post 
Pete,

I'll check for the 443.
In case there is the 443, I have few questions:

1. Should the pink noise recorded at -20dbFS?
2. Should the SUbwoofer pink noise recorded band limited?
3. I do not have the extender for the eq cards. Can I build it by my own? Can I remove the EQ cards while CP is powered (with just the fader set to 0)?

I hope that there is the 443, it will be my first equalization! [Smile]

Bye
Antonio

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Michael Schaffer
"Where is the
Boardwalk Hotel?"

Posts: 4143
From: Boston, MA
Registered: Apr 2002

- posted 11-19-2002 10:29 AM      Profile for Michael Schaffer   Author's Homepage   Email Michael Schaffer   Send New Private Message       Edit/Delete Post 
Probably not a very good idea, but in absence of other means, what about using the pink noise test loop for the slit loss to eq the left and right channel, then copy the settings to the center channel?

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John Hawkinson
Film God

Posts: 2273
From: Cambridge, MA, USA
Registered: Feb 2002

- posted 11-19-2002 01:45 PM      Profile for John Hawkinson   Email John Hawkinson   Send New Private Message       Edit/Delete Post 
At that rate, you might as well swap cards.

--jhawk

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Antonio Marcheselli
Phenomenal Film Handler

Posts: 1260
From: Florence, Italy
Registered: Mar 2000

- posted 11-19-2002 02:05 PM      Profile for Antonio Marcheselli   Author's Homepage   Email Antonio Marcheselli   Send New Private Message       Edit/Delete Post 
Pete,

I'm not familiar with the CP65 so I've read the manual to understand the B-Chain procedure.
Cat 443 is listed as a logic card that configures the CP for the selected format. It is not listed as optional.
Are you sure that Cat 443 is optional and needed for Digital inputs?

Ciao
Antonio

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Pete Naples
Phenomenal Film Handler

Posts: 1565
From: Dunfermline, Scotland
Registered: Feb 2001

- posted 11-19-2002 05:55 PM      Profile for Pete Naples   Email Pete Naples   Send New Private Message       Edit/Delete Post 
My sincere apologies.

When I typed Cat443, I should have typed Cat441. There is quite a difference!

If it doesn't have a Cat441, you can still do the 'B' chain via the 6 channel input, you just can't align Right Surround and Subwoofer, as there will be no Right Surround or Subwoofer output. As no card = no Rs/SW, then there's no need to worry about it's presence!

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Gunter Oehme
Film Handler

Posts: 17
From: Frankfurt, Germany
Registered: Jun 2000

- posted 11-19-2002 07:50 PM      Profile for Gunter Oehme   Email Gunter Oehme   Send New Private Message       Edit/Delete Post 
Antonio, Pete,
you can use the analog inputs for digital sound formats.
The pink noise signal should have a level of 380 mV RMS.

The limitation is that sub woofer input will be in digital mode i.e. +10 dB inband.
For setting the level of the optical (analog) sub woofer the 6 channel input cannot be used. For this purpose the pink noise signal needs to be injected at the connector of the Cat 441 on the backplane.

Pulling the Cat 64 for all adjustments make only sense if small corrections are needed.
However you could try move the pots while the Cat 64 is installed. Just remove the Cat 222 and 150 and use only one Cat 64 at a time.

Michael,
using the pink noise loop for slit loss film in the regular signal path is really not a good idea.
In mono format the academy filter is in the signal path.
In the Dolby formats the pink noise signal will be not linear after Dolby A or SR decoding.

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