my profile | my password | search | faq & rules | forum home

» Film-Tech Forum ARCHIVE   » Operations   » Film Handlers' Forum   » How to “calibrate” Perspect-A-Stereo card?

Author Topic: How to “calibrate” Perspect-A-Stereo card? Gary A. Hoselton Film Handler Posts: 59 From: Portland OR U.S.A. Registered: Nov 2005 posted 02-18-2018 06:59 PM                     Input is from Simplex 5-Star soundhead with reverse scan red LED into Component Engineering pickup, then thru CP-500, out Analog Accessory connector pins 35 and 37 Optical Right and Optical Left thru STA-1 stick-on amplifiers to Dolby SA-4 IN R and IN L, which go to Perspect-A-Stereo card inputs. The card’s outputs L, C, and R go to Analog Accessory connector ACCNRL, C, and R pins 19, 15, and 18, thence to a Perspecta User Format that Joel Miller programmed for me last summer. The Perspect-A-Stereo card is upside-down in the SA-1, has one red LED and four green LED’s under the board. I’ve come by some used Perspecta calibration loops, with fairly worn hand-lettered labels on masking tape as follows: A 400 Hz B 35 Hz high C 35 Hz low D 25 Hz high E 25 Hz low F 400 Hz 50% w/ 25Hz high and 35Hz low. I have no instructions for the Perspect-A-Stereo card, which has no adjustments on it. What do the LED’s indicate, and how do I use the loops with this card? My only adjustment now is gain in the STA-1 stick-on amplifiers.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 02-18-2018 07:46 PM                     The Perspect-A-Card requires NO calibration. The original tests were for the original "tuned" circuits. The RED LED lights when there are NO tones to denote it is mono and the card will pass the audio out of center. The next green LEDs indicate Left, Center and Right output. There is a 4th LED for surround, which was NOT part of the Perspecta process. However the card, if an extra jumper were soldered in, to allow a fake surround output if it senses all three signals are present. I've tried it; it wasn't a good effect. The card was designed to go into a Dolby processor in place of a CAT150 so it has input pins for 300mV and 500mV nominal levels and output at 300mV nominal levels. You want to hit the input levels as accurately as possible (I'd have to look up what the SA4 card cage is looking for...probably 500mV since it is a CP100 box) but I'd confirm, if I were you). Run Dolby-Tone to set the level, not your Perspecta loops. Once set, your loops should confirm that the card is decoding properly. Since Perspecta is tone level dependent, it is real important to get the input level right for the best results though it will still work to a degree if you are off (the tones control VCAs on the card to ramp the various channels up/down).  |  IP: Logged Gary A. Hoselton Film Handler Posts: 59 From: Portland OR U.S.A. Registered: Nov 2005 posted 02-25-2018 12:12 PM                     Thanks, Steve, I have it working. At my STA-1 stick-on amplifiers, I set each of L and R inputs to Perspect-A card at 500mVrms referenced to signal ground, threaded up a mid-50's MGM Droopy cartoon, and the red light went out and the L, C, and R green lights began going on and off. Most sound came from center speaker, I think because that is how the cartoon was staged, and beginning and end title music was splashed all across the screen.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 02-25-2018 01:34 PM                     Which make of card do you have  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 02-25-2018 02:18 PM                     In Germany they do Perspecta decoding with a DSP audio processor. It even includes the indicators for the control tones.... Mark  |  IP: Logged Gary A. Hoselton Film Handler Posts: 59 From: Portland OR U.S.A. Registered: Nov 2005 posted 02-26-2018 03:27 PM                     Gordon, I have the Perspect-A-Stereo card. I'm told it was made as a side project by some Dolby fellows in England.  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 02-26-2018 11:35 PM                       I don't know if the German ones are the same but a couple of Dolby London guys guys did the one you have. They've all retired by now.  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 02-26-2018 11:36 PM                       I don't know if the German ones are the same but a couple of Dolby Lodon guys guys did the one you have. They've all retired by now.  |  IP: Logged Marin Zorica Jedi Master Film Handler Posts: 671 From: Biograd na Moru, Croatia Registered: May 2003 posted 03-05-2018 04:14 PM                     For Germany, i think Mark is refering to guys from Karlsruhe cinema where they did programm BSS BLU dsp processor to do it.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 03-06-2018 09:00 PM                     Marin, You are correct.  |  IP: Logged

All times are Central (GMT -6:00)

Printer-friendly view of this topic

Hop To: Select a Forum: Category: Operations -------------------- Digital Cinema Forum Film Handlers' Forum Large Format Forum Ground Level Feature Info, Trailer Attachments & REAL Credit Offsets Category: Community -------------------- Film-Yak Film Handlers' Movie Reviews The Afterlife Bob Maar's Joke-A-Thon Category: Classified -------------------- Equipment and Supplies Wanted/For Sale Help Wanted/Seeking Employment Category: System -------------------- Software Beta Testing Forum

The Film-Tech Forums are designed for various members related to the cinema industry to express their opinions, viewpoints and testimonials on various products, services and events based upon speculation, personal knowledge and factual information through use, therefore all views represented here allow no liability upon the publishers of this web site and the owners of said views assume no liability for any ill will resulting from these postings. The posts made here are for educational as well as entertainment purposes and as such anyone viewing this portion of the website must accept these views as statements of the author of that opinion and agrees to release the authors from any and all liability.