Film-Tech Forum ARCHIVE: help? CP45 + X-men = blech

This is topic help? CP45 + X-men = blech in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=009901

Posted by Dave Macaulay (Member # 813) on 05-20-2009, 05:26 PM:

Hi again.
Smallish house with a CP45 and CE analog reader, passive crossover speakers (JBL) and USA900 amps.
Sound is fuzzy especially on right channel. It is audible on my trailer test reel but I would say not objectionable, but there isn't much except loud sound on the trailers.
On X-men Origins the sound is really bad, lots of distortion in the right channel particularly. Most serious with speaking level, explosions etc just sound loud as usual.
SO far I've changed a bad amplifier (fan gummed up, thermal cutout every few minutes - but sounds OK), the CP45, and the CE reader unit. The distortion stays with the amplifier channel, ie the speaker itself is OK. Sound is fine in mono ("enhanced mono" using LCR). Sounds better in "A" than SR.
I know the CP45 SR is unexcellent, but this is beyond the usual 222 SR/A fuzziness.
The only thing I have not changed so far is the CE red LED or power supply.
Dolby tone, buzz/LR, and pink noise look and sound OK.
NS sounds OK.
I changed out the processor thinking the matrix must be going screwy. Today was rather frustrating when the dang thing still sounded bad.
The cinema swapped X-men to another house and they say it sounded fine (another CP45) but I wonder about the print anyway.
Any ideas before my next visit? I'm kinda low on them now.

Posted by Gordon McLeod (Member # 33) on 05-20-2009, 08:26 PM:

I have had the readers particularly the solar cell go bad usually it starts with a lot of distortion and then fails
try running jiffy on it
Also run the cat 97 l/r film and look at thel and r outputs in SR with a scope

Posted by Scott Christopher (Member # 834) on 05-21-2009, 12:02 AM:

Years ago I had problems with the booster pre-amp being faulty on one of our readers. From memory, It was the either the TL-072 or TL-074 op-amp on board.

Posted by Dave Macaulay (Member # 813) on 05-21-2009, 06:28 AM:

Agreed the reader seems to be a likely suspect. I've tried two others: a shop spare and one from another system at the same cinema that sounded fine.
Is there any way the actual LED array could cause noise and "fuzzy" distortion in the audio?

Posted by Gordon McLeod (Member # 33) on 05-21-2009, 08:32 AM:

If some of the actual LED segments have failed it will be very distorted

Posted by Kenneth Wuepper (Member # 1174) on 05-21-2009, 08:43 AM:

Dave,
I don't understand your last post. Did the two other readers clear up the problem or is the sound still bad in the right channel?

In answer to your question, missing or dark segments of the LED array can cause distorted sound. It looks to the reader like there is no information in that area of the sound track. At certain levels where the volume places peaks of information in the dark area, it will sound like the track is clipping, as they are not scanned. Lesser or greater volumes will have some distortion but will not exhibit the clipping as described above.

KEN

Posted by Dave Macaulay (Member # 813) on 05-21-2009, 04:27 PM:

Neither swapped reader fixed it - the shop one wasn't definitely good, the one from another cinema was at least sounding OK there.
I will take a new LED and inspect the array to see if there are dark spots. I can see if a segment is dark near a channel track centre line then low level sound would be distorted. I did, however, realign the LED for best output level and recentred it on the sound track by eye with a mirror. The sound problem didn't change then.

Posted by John Hawkinson (Member # 1135) on 05-21-2009, 06:54 PM:

Perhaps a use for that otherwise-unused Cat. 566 uniform illumination test film.

--jhawk

Posted by Pete Naples (Member # 761) on 05-22-2009, 11:43 AM:

quote: John Hawkinson
unused Cat. 566

Whit?! It's one of my most used!