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Topic: Non sync level on a CP50

Tom Kroening
Expert Film Handler

Posts: 214
From: Janesville, WI USA
Registered: Oct 1999

posted 03-16-2002 01:12 PM

Hey everyone. We're currently having a few video projectors hooked up for ads. The guy thats doing the install can't seem to get the nonsync level down in one of the houses. I verified that the non sync pot is turned all the way down, yet the sound is still coming out really load. All I can think of is to get something to go inline with the preamp signal from the dvd player (like a volume adjuster on a set of headphones). I haven't taken a close look at it yet, but I will be tonight. Does anyone have any suggestions? Or maybe this has happened to you before? I don't think the CP50 was designed in mind with being hooked up to a DVD player to begin with

but hopefully we can get it to work. Thanks!

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Scott Norwood
Film God

Posts: 8146
From: Boston, MA. USA (1774.21 miles northeast of Dallas)
Registered: Jun 99

posted 03-16-2002 01:19 PM

Which switch card do you have? The cat. 113c "automation" card that uses a little screw to adjust the non-sync level or the regular cat. 113 with the mechanical pushbuttons that has a large knob for adjusting the non-sync level?

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Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 03-16-2002 03:04 PM

Too much time has passed with me and CP50s for be of much assistance here from memory (and I don't have access to look at one for a memory refresher), but I do recall seeing that a LOT of CP50s had their non-sync wired through projector 2 of the optical preamp card for various reasons, others inputted the signal into the magnetic inputs. Can you verify which input is being used?

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Steve Kraus
Film God

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

posted 03-16-2002 04:09 PM

The standard CP-50 switch card with mechanical pushbuttons is Cat.112 and has no volume control for the non-sync/mag input. It simply switches this input directly to the amps. No volume, no EQ, no nuthin. If the source device does not have an output level control you must create one with a potentiometer mounted somewhere on the soundrack.

I can't see any reason to hook up to the optical input unless for some reason the level is so low it can use the added boost. Perhaps people did this as a quick and dirty alternative to wiring up a non sync level pot?

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Tom Kroening
Expert Film Handler

Posts: 214
From: Janesville, WI USA
Registered: Oct 1999

posted 03-16-2002 04:24 PM

It is the newer automation card. I'll have to check all the inputs on the back when I go in tonight. Does anyone know where I would get such a device that could lower the preamp signal before it gets to the processor?

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Steve Kraus
Film God

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

posted 03-16-2002 05:09 PM

Are you handy with a soldering iron? A 100K, dual gang (stereo) pot from Radio-Shack, etc. would do the trick. Wire it so that the "hot" signal lines from the source are connected to the ends of the potentiometers that the wiper reaches when turned to maximum clockwise while the counter-clockwise ends are each connected to the common / ground. Thus, the wiper sweeps across a range running from ground to full power. It's odd that you can't control it with the existing control but this should reign it in.

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Jon Bartow
Master Film Handler

Posts: 287
From: Massachusetts
Registered: Nov 1999

posted 03-16-2002 08:58 PM

Please don't be offended, but do you have the external fader connected? The CP50 needs a 100K linear taper pot connected to control the main "volume" (or one of Dolby's external fader boxes)
If you don't have the pot connected than IIRC the volume is at max and your 300mv+ signal from the DVD would be very loud.

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Gordon McLeod
Film God

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

posted 03-16-2002 10:11 PM

For the audio from the nonsync to be routed throught the fader the daugther board on the backplane is requried

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Tom Kroening
Expert Film Handler

Posts: 214
From: Janesville, WI USA
Registered: Oct 1999

posted 03-17-2002 04:42 AM

I think you guys hit the nail on the head. The external fader might be hooked up wrong, although it works for the main volume. To solve the problem I just went to radio shack and got one of those inline headphone volume adjusters, put RCA cables on each side and pluged it into the audio output of the DVD player. 20 dollar solution that saved me from messin with that old dinosaur. Hopefully she keeps workin! Thanks everyone.

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Gordon McLeod
Film God

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

posted 03-17-2002 12:00 PM

Well I doubt the fader is wired wrong if it works as the main fader
One must remember how the processor was designed to be inserted into an exisitng 4 track mag system

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Peter Hall
Master Film Handler

Posts: 314
From: London, UK
Registered: Dec 2000

posted 03-28-2002 12:07 PM

HI -

The CP50 Cat 113C non sync level control is hopeless - a standard CD player blasts the audience out of their seats. But a CP50 even with a Cat113C does (from memory) not use thte main fader to control the non sync input. Assuming you're coming off DVD (as you said, the CP50 was not quite designed with a DVD in mind - in those days - I was still in school (!!) - CD's weren't in widespread use !) and using the LtRt outputs of the DVD wouldn't you want to utilise the matrix in a CP50 ? Once again from memory if you mod the CP50 as if it were receiving a SRA5, then hack into the return path from the SRA5 to the CP50 you'd achieve this. Select SR - return path would go thru the Cat150 with no NR. You'd still need to screw around with levels to get the ideal 300mV however.

Good luck

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Steve Kraus
Film God

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

posted 03-28-2002 03:51 PM

It is possible to introduce line level LtRt signals at a number of points on the CP-50 including at the stage of the 110L/160 slot just before the Cat.150. I'm not sure it makes sense to run this material through the matrix though, unless it was mixed with matrix playback in mind. Otherwise it may just bunch up on C. You'd have to listen to it and decide whether the normal, direct way is ok or whether it's worth the trouble to get it through the EQ cards (and fader).

Are CD (and DVD) player outputs not line level?

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Gordon McLeod
Film God

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

posted 03-29-2002 11:56 AM

On the back plane one could connect to the preamp out terminals but the otpical preamp would have to be removed first or to the terminals marked external surround adapter but the before hand cards should be unplugged
Some electronic devices don't particularly like a signal flowing back into there outputs

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System Notices
Forum Watchdog / Soup Nazi

Posts: 215

Registered: Apr 2004

posted 10-18-2008 01:43 PM

It has been 2395 days since the last post.

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Dominic Espinosa
Phenomenal Film Handler

Posts: 1172
From: Boulder Creek, CA.
Registered: Jan 2004

posted 10-18-2008 01:43 PM

I have a dumb question...

I'm currently going into a CP50 from a DVD players stereo out via the projector 2 input -- works pretty well.
But I wonder if perhaps I could take advantage of the free mag input/would it be worth the trouble?
Is there a cheapish way to control the volume for the mag input?

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