Film-Tech Forum ARCHIVE: Dolby CP45 and non sync 2 i/p

This is topic Dolby CP45 and non sync 2 i/p in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Alexander Smith (Member # 1769) on 11-23-2003, 06:18 PM:

Inspired by the thread recently where it was said an external AC3 decoder could be connected to a CP45 via the non-sync 2/aux i/p: I set up my Creative Extigy to do the same.

I realise that without a CAT515 in the CP45 I won't get split surrounds but that's not important for this exercise.

I checked and double checked the wiring, but there was still no centre channel signal from the CP45. Left, Right, Sub and surrounds: Good. I was playing a DVD as a test, making sure that there was supposed to be dialogue.

Connecting a stereo pair of speakers to the centre/sub output from the Extigy gives (predicatably) the centre channel on the left speaker, and the sub on the right speaker. The problem isn't the Extigy. I've also checked the Extigy is decoding for full 5.1 output (not 4.0).

Suggestions please... I've not had time to try this with a different CP45 (we have four), but my spare time is limited.

I have a show coming up where I will need to use this set-up, but the show only needs Left and Right repro. I suppose I could use the non sync 1 i/p on the CP45 and set the jumpers for matrix decoding.

Alex.

Posted by Peter Hall (Member # 695) on 11-24-2003, 08:42 AM:

Stupid question - is the DVD or decoder set to phantom centre??

Posted by Alexander Smith (Member # 1769) on 11-26-2003, 02:20 PM:

The Extigy was definitely decoding for a real (not phantom) centre channel. I checked by connecting
the Extigy to my laptop via USB so that Creative's own control software could access it. Also, in a test
away from the CP45 there was a centre channel o/p.

Alex.

Posted by Manny Knowles (Member # 1171) on 11-27-2003, 12:09 AM:

It would really help to have more details...

Am I correct in assuming that your DVD player has onboard decoding?

I wonder if you are using modified consumer cables -- RCA with one end stripped -- in order to tie into the NS2 phoenix connector on the CP45?

I have done this before and it worked but the levels were a little low. Some method of boosting the signal would have made my day. Still, it worked.

Posted by Pete Naples (Member # 761) on 11-27-2003, 03:13 AM:

*cough*

Posted by Manny Knowles (Member # 1171) on 11-27-2003, 03:20 PM:

Pete? R U O K ?

Posted by Alexander Smith (Member # 1769) on 11-29-2003, 08:23 PM:

In answer to Manny's questions:

I'm allowing the Extigy to decode to analogue outputs (I think that's what Peter was hinting at
with his *cough*)

The cables I made up from scratch, although I've already tested those, even down to swapping
left and centre at the CP45 end, and hearing the centre signal come from the left speaker.
The levels were good, apart from the centre of course.

Alex.

Alex.

Posted by Manny Knowles (Member # 1171) on 11-29-2003, 10:46 PM:

What happens if you activate the pink noise generator in the CP45?

Hold down the Format 04 and 05 buttons together for about 7 seconds until pink noise is heard coming from the Left channel. The Microphone selector LED will flash and the pink noise will cycle between L, C, R & (mono) Surrounds.

Listen and compare the level of the pink noise for the center channel versus the others. Is the center channel quieter or do the levels match up? If your centre channel gives you matching level on the pink noise then you can rule out any problems with your CP45 output and also your amps and speaker connections.

In addition to the pink noise test, I would also like to know what happens when you try to play the Left channel of your DVD through the Centre channel of NS2. If you still get nothing then I would say you've got trouble at the NS2 input or maybe a little deeper into the processor.

Posted by Manny Knowles (Member # 1171) on 12-05-2003, 03:57 AM:

Just curious as to the status of this situation..?

Posted by Alexander Smith (Member # 1769) on 12-05-2003, 09:30 PM:

Sorry for not replying sooner, had a very busy week.

Back to the topic: We've had all our sound systems put through a full A chain re-alignment and
B chain re-equalization. Part of our service contract e.t.c.

If the centre channel _was_ a little on the quiet side, it will be correct now. I'll post again once
I've had chance to follow Manny's suggestion and do some more re-tests.

Alex.

Posted by Alexander Smith (Member # 1769) on 12-11-2003, 06:58 PM:

Ok, finally managed to squeeze in a little bit of further testing this week. I found the centre channel
_is_ being passed from the NS2 i/p to the centre speaker, but at a very low level. I had to turn the
fader up to 10 to hear it.

Also, I tested another CP45 (so far I've been using the same unit), and got exactly the same results.

Is this "normal" for a standard CP45, is this caused by the CAT515 board not being present?
If someone from Dolby is lurking, now would be a good time to speak up. ;-)

Alex.

Posted by Pete Naples (Member # 761) on 12-11-2003, 07:30 PM:

Alex, this all sounds odd! I've done exactly what you are trying to do, ok the DVD player had an on board decoder but that's of no consequence. But the CP45 I was connecting to DID have CAT 515 fitted....
I just had a look in the CP45 book, according to the signal flow diagram, centre has nothing to do with the CAT 515, however I have found in the past that the signal flow diagram in the manual was not entirely accurate.....
Sorry I can't be of more help right now, have you tried calling or emailing Steve? He may be able to help.

Posted by Alexander Smith (Member # 1769) on 12-13-2003, 07:10 PM:

For the benefit of the lurkers, I've taken this to email with Peter.

I'll post a summary of the results, for completeness's sake.

Alex.

Posted by Alexander Smith (Member # 1769) on 12-28-2003, 03:47 PM:

Result! I traced the problem to me not clamping the signal cable properly
in to the Phoenix connector. I had clamped the insulator (d'oh!), so the
cable appeared to work when laid flat on the bench, but when connected
to the CP45 as the wires hung out the back it didn't work.

Ho hum. Now to wait for the next video show we do for local, low-budget
film-makers.

Posted by Manny Knowles (Member # 1171) on 12-28-2003, 04:29 PM:

Thanks for giving us closure -- and just in time for year's end, too!