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Author Topic: Setting output on Dolby processor Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 05-12-2010 05:22 AM                        Calibration was necessary when Bill Purdy owned the company. In fact there was a letter with the unit saying so. Louis  |  IP: Logged Tom Wienholt Master Film Handler Posts: 371 From: Towson, MD, USA Registered: Dec 2002 posted 05-12-2010 08:59 AM                     That's interesting. I purchased the generator about 8 years ago and don't remember anything in the package stating that calibration was necessary. Is this something that can be done on my own? If so, what is the process?  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 05-12-2010 09:01 PM                        Not to be glib, BUT. . . . Borrow a Dolby pink generator and set up for 85dba. Remove Dolby and insert your generator. The small screw (at bottom, I think.) turn until you get the same reading. Louis  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 05-12-2010 09:09 PM                     Yea, that's what it was (for I've forgotten the technique) why I didn't post on how to calibrate the SG-1..now, good to know. thx-monte  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 05-13-2010 12:15 AM                       The output level is supposed to be 300 mV with a true averaging meter, not RMS. The exact number is 287 mV I seem to remember, but who has a true averaging meter? Steve will be along to enhance or correct me by sunrise.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 05-13-2010 08:43 AM                     quote: Louis Bornwasser I turn the amps full up and set Dolby to 85dba, see book. Thats fine on amps that have 2.0V for full output. But on amps that are 1 volt for full out you may hear too much background noise from the electronics. I remember that Sam taught us in Dolby training to turn the output of the amps down and the Dolby up to a slightly higher level to effectively mask the electronics noise or increase the S/N ratio. of course this was the CP-50 days. I still do this for USL S Series which can be noisy. Works well. The 650 is much quieter.  |  IP: Logged Sean McKinnon Phenomenal Film Handler Posts: 1712 From: Peabody Massachusetts Registered: Sep 2000 posted 05-13-2010 12:03 PM                        If one wanted to use a soundfile of pink noise on a laptop to set SPL for video sources/external inputs how should you set the output level of the laptop? Run the pinknoise and measure the output with a meter? Should it be set for 300mv, or 775mv? or something else all together? What I am trying to acheive is to have our "simulcast" system set properly so that content in one house that is played at "7" has the same level at "7" in the other house. We are sending embedded digital audio with an HD-SDI signal and the audio embedder has it's own level adjustment that I can use to raise or lower the signal level being sent.  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 05-13-2010 12:25 PM                       300 mVolts is Dolby Buss level but hard to measure accurately with digital meters looking at pink noise. The detail I've forgotten is Subwoofer level but I believe it is also 300 mVolts.  |  IP: Logged Chase Taylor Expert Film Handler Posts: 175 From: Troy, Alabama, USA Registered: Mar 2001 posted 05-13-2010 03:43 PM                        How do you measure the output to 300mv if you are useing an internal crossover like in a CP-500?  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 05-13-2010 05:20 PM                       I thought we were talking about input to the processor. The 650 has a low and high gain setting inside if I recall correctly. Its meant to optimize 650 noise floor vs. clipping threshold.  |  IP: Logged Christos Mitsakis Expert Film Handler Posts: 242 From: Ag.Paraskevi, ATHENS, GREECE Registered: Sep 1999 posted 05-13-2010 06:17 PM                     Sean, sometime in the past, Gordon gave a nice solution: quote: Gordon McLeod: A solution would be play dolby tone and set the out put of the center channel (when in stereo A) to 300 mv Then inject your pinknoise source and adjust it's level to match that output then do the rest of the channels I hope this helps C.  |  IP: Logged Sean McKinnon Phenomenal Film Handler Posts: 1712 From: Peabody Massachusetts Registered: Sep 2000 posted 05-14-2010 09:13 AM                        Thank you Christos (Gordon) and Sam! I have been doing something similar to gordons method where I have been setting the processor to "7" and measuring the SPL in the house of the internal pink noise at that fader setting. Then I connect my Laptop directly to the processor and play pink noise while adjusting the level on the laptop until I get the same SPL as I did with the processor's internal pink noise. After that I connect the laptop to the SDI embedder and adjust the levels on that until I get the same reading I got from the internal pink noise. It seems to match everything pretty well I just wanted to know if there is a more correct way.  |  IP: Logged

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