Film-Tech Forum ARCHIVE: Format 11 Vs Format 22 on CP650

This is topic Format 11 Vs Format 22 on CP650 in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Don Furr (Member # 1469) on 07-31-2017, 09:14 PM:

Using Format 11 (6 channel input) I'm able to play the four channels from my 35mmm mag reader. I set up U1 for Format 22 which displays "4 Channel Mag Stereo) The problem is the surround track will not play.
What am I missing?

Posted by Steve Guttag (Member # 268) on 08-01-2017, 07:10 AM:

A 12KHz pilot tone to turn the surround channel on? Is the print you are playing absent from having the pilot tone?

Posted by Don Furr (Member # 1469) on 08-01-2017, 07:51 AM:

Steve I'm using a Smart 435 preamp which doesn't have the 12hz tone capability like the older 430 preamp. Using Format 11 the surround channel is constantly present.

Posted by Steve Guttag (Member # 268) on 08-01-2017, 09:45 AM:

The tone is on the film. If the preamp is passing the tone to the CP650, then it would be up to the CP650 to turn the surrounds on/off based on that tone.

That said, I have never configured the CP650 for format 22 so I don't know if that is the issue or not but when I hear no surrounds, then I think the pilot tone is not being triggered to turn them on.

Posted by Mark Gulbrandsen (Member # 72) on 08-01-2017, 01:57 PM:

You ought to get your self a real Dolbly MPU and get rid of the Smart thingy. The Smarts never had any bottom end response to them. If you hunt around you might even find a 12khz switching card for the Dolbly MPU.

Mark

Posted by Sam D. Chavez (Member # 1841) on 08-01-2017, 04:43 PM:

The 12Khz card is rather rare for the MPU. Mostly they were sold for 70mm and even though there is a card bay for 35mm Cat. No. 92's is was usually not purchased with that card. Often they there were fitted with a 12 Khz bypass card.

I look forward to hearing the answer to why the surround channel is not getting through as well.

Posted by Don Furr (Member # 1469) on 08-04-2017, 04:49 PM:

Back on this project after 3 days out of town.

Steve....I was not aware that the CP650 had the ability to detect the 12Khz tone and turn it on/off.

Mark....I had the complete Dolby MPU with the card and sold it a couple of years ago.

Sam....I hope to get to the bottom of this issue soon.

Posted by Steve Guttag (Member # 268) on 08-04-2017, 04:54 PM:

Don, I don't know for sure that the CP650 does decode the 12KHz tone, it was just a gut reaction to the symptoms you described. I'd have to research it to get a definitive answer.

Posted by Mark Gulbrandsen (Member # 72) on 08-04-2017, 05:33 PM:

You should buy that Dolby MPU back!The Smart is a POJ....

Mark

Posted by Don Furr (Member # 1469) on 08-04-2017, 11:37 PM:

So here's a quote from the operator's manual for the CP650:
Format 22

35mm Composite Magnetic 4-Track
Standard 4-track, no NR, magnetic filter

Is it possible that the term "magnetic filter" suggest there is a 12Khz filter build in the processor?

Posted by Steve Guttag (Member # 268) on 08-05-2017, 04:45 AM:

No. The magnetic filter means that it applies a reduced form of the Academy filter to knock down some of the highs/lows to "Conventional" magnetic prints without Dolby NR.