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Author Topic: Panastereo opt. preamp. Rob J. Buskop Expert Film Handler Posts: 111 From: Rotterdam, the Netherlands Registered: Aug 2005 posted 09-20-2016 08:56 AM                     I have to extend my compliments to the memory of Mr. Chavez. When I got interested in the CP-100 in 1992, one of the first things that became apparent was the "less than ideal.." design of the preamps indeed. What was even more unpleasant than the crosstalk, was the fact that the designer(s?)had introduced a HF feedback set-up that effectively at higher gains worked like a positive feedback, with strong oscillation tendencies. If you pushed it a little bit.., wham!.., there it went with the meters jumping against the stops. Awful. That's when I started with the new design, based upon the principle of the inverting preamp or current to voltage schematic as also done by Kintek some time before. The end result as shown above is working flawlessly, but as we designed it in 1993 (!), the academic question is: Is there any improvement attainable by implementing later design philosophies? How does it compare to Cat.240 & 240A or Panastereo's performance? I'm now in the process of trying to get an analytical answer from Delft Tech University where they might be willing to me a favor and do a computerised analysis of the different designs. I'm going on a 2 week holiday now, but will continue this quest on my return and will keep you posted on eventual outcomes of interest. All your imput has been highly appreciated. Thank you!  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 09-20-2016 11:33 AM                     For those wondering what the Panastereo preamp is here is a picture of the little jewel... Any collector that is truly serious about film sound should seek out an entire CSP-1200 processor. Not just the preamp card. There is way more to it than just this single card!!  |  IP: Logged Fabian Schreyer Film Handler Posts: 63 From: Aachen, Germany Registered: Feb 2009 posted 09-21-2016 03:20 AM                     By the way: How do the Cat. 108-4 and 108C compare? I have always been told that the C-version would be a HUGE step from the 108-4.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 09-21-2016 07:12 AM                     The depending on who's findings your believe from above...your results may vary. The big change is the ground plane fill. There were also some loading resistors added to the output of the preamp but the essentials of the it remain unchanged. I think they reworked the slit loss correction slightly to be be more friendly to reverse scan readers (flatter response).  |  IP: Logged Rob J. Buskop Expert Film Handler Posts: 111 From: Rotterdam, the Netherlands Registered: Aug 2005 posted 09-21-2016 08:48 AM                     Thanks Mark for posting that nice picture of the Panastereo preamp card. Does it work as a transformerless balanced input? I suppose it does. Of course I fully agree with your statement that this is just a part of a, as a whole, superior system. In this case however I'm just trying to find out about the possible design- and performance differences between a group of optical preamps. I think I've located Mr. Ray Derrick and hope he'll be able to supply me with a schematic so we can do a full scale comparison as planned. Have the schematics of the Cat.240 and the 240A, so with the Panasound's and my Kintek adaptation we have four examples of different pedigree. Very interesting!  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 09-21-2016 09:57 AM                     It is balanced input with no transformer and treats the cell as a current source so it has verey low distortion  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 09-23-2016 08:50 PM                     I looked at a 108-4...didn't find the feedback compensation circuit. Well played Mr. Chavez. The layout of the 108C is also radically changed (and done via computer) versus the original 108.  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 09-25-2016 12:26 PM                       Thank God my memory served me well this time.  |  IP: Logged

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