This is topic Pink Noise Generators in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Dave Cutler (Member # 515) on 07-11-2000, 10:53 AM:
I am thinking about buying a pink noise generator (used cat 69p up till now) and had a few questions. Is there a difference between the Dolby and the Ultra Stereo, and are there any advantages to either? Can one work in both companies processors? What is the cat number for the Dolby? Ultra Stereo is the JPN-10, right?
Posted by Brad Miller (Member # 2) on 07-11-2000, 02:33 PM:
Dolby's will only work in Dolby processors.
Ultra's will only work in Ultra processors.
Posted by Aaron Sisemore (Member # 145) on 07-11-2000, 10:48 PM:
Dolby's generator is Cat 85C it works with the following processors:CP50
CP55
CP65
CP100
CP200
The CP45,CP500, and I will assume the CP650 have a built-in pink noise generator...
Aaron
Posted by John Walsh (Member # 168) on 07-12-2000, 09:12 AM:
A tech here really likes the Component Engineering SG-1 pink noise generator. It is meant to work with only the Dolby processors, though. Strangely, there's no info on their web site about it.
http://www.componentengineering.com/
Posted by Bill Purdy (Member # 202) on 07-12-2000, 10:06 AM:
But there will be in about 24 hours! The SG-1 is still available and is plug compatible with Dolby's Cat. No. 85. It offers smoother pink noise (the low end doesn't "gallop"), sweep sine wave oscillator which is handy for finding rattles, connection for remote On/Off when making reverb measurements, and a handle for pulling it out of the slot. (It also has Red Noise, but let's no go there.) It sells to anyone for $280.00.------------------
Bill Purdy
Component Engineering
Posted by Gordon McLeod (Member # 33) on 07-13-2000, 10:20 AM:
Also the Ce one is the only one that works with the Eprad DSS processors
Posted by Tim Reed (Member # 137) on 07-13-2000, 04:59 PM:
Bill, I love my CE p.n. generator! That oscillator is a blessing!------------------
Better Projection Pays!
Posted by Scott Norwood (Member # 30) on 07-13-2000, 05:48 PM:
Red noise?!?! What's that?
BTW, how bad would it be to use the pink noise test film instead of the proper pink-noise generator card? Assume a proper soundhead alignment, of course.
Posted by Francis Casey (Member # 514) on 07-13-2000, 08:16 PM:
I use the Dolby Cat 85c and the Ultra Stereo JPN10 both are accurate and work well in their respective processors .
I also use a very conpact and functional signal generator made by Neutrik ; Check it out at the address below . http://www.neutrikusa.com/products/test_equipment/index.html
It is called an MR-1 Minirator
Also check out the ML-1 Minilyser
This looks to be a very sofistacated audio analyzer-- I have one on order .
Francis
Posted by Gordon McLeod (Member # 33) on 07-13-2000, 08:32 PM:
i used the 85c for years till I bought one of the CE's from Bill himself at Showwest the year he introduced it
I have never used the 85c again
the 85c is a noisy transitor compared to the ce
Posted by John Walsh (Member # 168) on 07-14-2000, 09:16 AM:
(Tapping my foot..) Mr. Bill Purdy, it's been more than 24 hours. Where's that info on the pn generator. Young man, how can we learn how good it is if we can't see it?Also, I just have to ask. What is red noise? Some sort of extreme high freq. roll-off? How does that help an installer?
For a dictionary of audio terms, goto:
http://www.rane.com/digi-dic.htm
Posted by Bill Purdy (Member # 202) on 07-14-2000, 10:06 AM:
Look again---our web master, Brian Long, had to first find the photo, scan it and all that jazz and still keep up with being in charge of production. He assures me that it was there with 15 minutes to spare!OK, what is Red noise? You start with white noise which is what the basic generator creates. Then, because each higher octave in the spectrum has a bigger chunk of it (it's only a change of 100 cycles to go from 100 to 200, but it is a change of 1000 cycles to go from 1000 to 2000), you have to modify the curve so that you can have that straight display you want. This adjustment wants to be at the rate of 3 dB per octave. The easy way to do it would be with one Resistor and one Capacitor, but this combination produces a 6 dB roll off, and for reasons I don't know this is called Red Noise. Therefore, the 3 dB roll off (which in our case takes a 7 pole filter), which is half way, is Pink Noise. Cute huh?
The Red Noise is in the generator because in the early days of the THX project there were still a lot of older Altec speakers in use and when the certifying tech was doing his reverb measurements there was the fear that the high frequency driver might be blown. So, use the Red Noise with its lower high end component and adjust the results.
For those who like the USL generator, there is a reason. Jack Cashin bought the rights to our basic generator circuit from us.
There is a little trick for those who use phase checkers that you might like to know about. If you put the "Noise/Tone" switch in the mid or "Off" position you can feed your phase checker output into the Output test jacks (the Blue one and Gnd) and it will appear at all of the channel selector switches so that you can use them to assign the signal. I wish I could say that it was planned, but it was pure serendipity.