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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 09-15-2016 11:44 AM      Profile for Rob J. Buskop   Email Rob J. Buskop   Send New Private Message       Edit/Delete Post 
Have some 20 years ago developed new preamps as replacements for the oldies in my CP-100. Have based the design on the Kintek's with the trans impedance inverting opamp. This has served me very well. Excellent roll-off correction and very stable with a huge gain range. A while a go I had some weird "hesitating" level with the symphonic play-out of an SR movie. (House of the spirits). Somebody suggested to try another preamp, so I temporarily inserted a cat.240A into the A chain. The lack of level-smoothness was about te same, but while exactly regulated on the analyser like the fromer preamp, I detected a somewhat clearer sound (piano!) and a slightly less bass area. Amazing since the analyser readiings were duplicates of each other. Anyway that set things in motion again: Should I consider doing another mod? SR has always been "noticeable" to me for it's clear signal processing and non-ideal smoothness. Remember that Mark G. always raved about the Panastereo preamps. Does anyone have a schematic of these? It's a bit like going back to the old hi-fi days when we compared carts, preamps and speakers and had long discussions about all this. So...: Back to the old days. Love to hear your ideas and commentaries!
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Rick Raskin
Phenomenal Film Handler

Posts: 1100
From: Manassas Virginia
Registered: Jan 2003


 - posted 09-15-2016 11:53 AM      Profile for Rick Raskin   Email Rick Raskin   Send New Private Message       Edit/Delete Post 
Please insert a bracket [ before the IMG tag so we can see the picture.

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Rick Raskin
Phenomenal Film Handler

Posts: 1100
From: Manassas Virginia
Registered: Jan 2003


 - posted 09-15-2016 01:44 PM      Profile for Rick Raskin   Email Rick Raskin   Send New Private Message       Edit/Delete Post 
Thanks

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99


 - posted 09-16-2016 05:16 PM      Profile for Mark Gulbrandsen   Email Mark Gulbrandsen   Send New Private Message       Edit/Delete Post 
No, I do not have any schematics Bob. Sadly those retired with Norm Schneider of Smart. I do however have a Panastereo CSP-1200 here in my home system. I can post any pictures you want. You might also contact Ray Derick who was the designer of it. He is on Facebook and lives down under. I can't say if Ray can even tell you what's in them or supply schematics or not since that entire product line was sold to Smart Devices.

Also, it's not JUST the preamp stage that's good sounding. It's the unit as a whole and in particular the SR noise reduction. It still has no equal to this day for overall sound or build quality.

Mark

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Scott Norwood
Film God

Posts: 8146
From: Boston, MA. USA (1774.21 miles northeast of Dallas)
Registered: Jun 99


 - posted 09-16-2016 05:23 PM      Profile for Scott Norwood   Author's Homepage   Email Scott Norwood   Send New Private Message       Edit/Delete Post 
quote: Rob J. Buskop
It's a bit like going back to the old hi-fi days when we compared carts, preamps and speakers and had long discussions about all this.
Don't people still do this? I have met a few 78 collectors and they are a particularly picky bunch, since the playback hardware characteristics had not yet been standardized when those records were made. It is truly amazing how good some 1940s recordings can sound when played back on modern, high-end equipment.

(Now back to your regularly scheduled film discussion....)

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Mark Gulbrandsen
Resident Trollmaster

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From: Music City
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 - posted 09-16-2016 09:13 PM      Profile for Mark Gulbrandsen   Email Mark Gulbrandsen   Send New Private Message       Edit/Delete Post 
quote: Rob J. Buskop
It's a bit like going back to the old hi-fi days when we compared carts, preamps and speakers and had long discussions about all this.
Yes, people still do this and there is an entire high end audio industry out there.

Mark

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Rob J. Buskop
Expert Film Handler

Posts: 111
From: Rotterdam, the Netherlands
Registered: Aug 2005


 - posted 09-17-2016 04:47 AM      Profile for Rob J. Buskop   Email Rob J. Buskop   Send New Private Message       Edit/Delete Post 
Yes, and is'nt that wonderful! Have a few friend who are really deep into that. Have a Technics SL-15 myself...From what I wrote you can rightfully deduct that I'm still deeply attached to my CP100. With it's discrete, very neat wiring it allows you to alter or add functions elegantly. Also interesting to find the odd error where for example the schematics are correct and the PCB layout proves to be faulty... Correct these things and wow.. it's even better! In the end I find it a lovely analog processor that, with the mods and additional functions I put in, does everything I want it to do beautifully. Anyway, I'm always in for some tweaking of the system and that's why I started this post. Thanks Mark for your reply. At some time in the past you mentioned that you had experienced a fairly large difference in the characteristics of the cat.240 and the cat.240A. Could you possibly elaborate a little bit more on that? One thing I personally like about the Kintek design approach is that they've designed the roll-off correction with a standard steepness (which is right of course) and one just moves the roll-off point along the 0 dB line and in doing so one chooses where the standard boost has to start and in doing so gets a perfectly straight response. With the Dolby approach, the roll-off point is fixed and the amount of boost is adjustable, which with a somewhat older standard reader always gives a bump at around 8kC. The inverting amp idea is also good although they've put a R of 330 Ohm in series with the inverting input... These things have a huge gain and a pre-pre for red light in not necessary. There's ample amplification available.
Do any of you have experience with sonic differences between the
afore mentioned pre's and possibly others?

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999


 - posted 09-17-2016 07:31 AM      Profile for Steve Guttag   Email Steve Guttag   Send New Private Message       Edit/Delete Post 
The biggest difference I remember in the CAT240 and CAT240A was the switch from a transformer based input to an active based input. As for Panastereo, it was the best preamp I worked with. You could get ruler flat responses and even when setting up Azimuth, you'd get better straighter lines on PN.

The preamps are around (inside CSP1200s) and Ray Derrick is as well (both here and on Facebook). It is definitely worth looking at, if you like to tinker.

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Sam D. Chavez
Film God

Posts: 2153
From: Martinez, CA USA
Registered: Aug 2003


 - posted 09-17-2016 12:59 PM      Profile for Sam D. Chavez   Author's Homepage     Send New Private Message       Edit/Delete Post 
Main difference between the 240 and A version is the active balanced front end vs. the transformer on the earlier version. It's quite an esoteric design but don't notice any sonic improvement.

I just did a project in an old movie palace that used Component Engineering readers with a CP65, 4 projectors. Old electrical power, different panels, etc., no real electrical ground. The CE reader would hum when used with a 240A but was totally happy with the 240. Tried all sorts of tricks to dodge the problem. No luck at all. There's no substitute for a transformer for true isolation.

The CP100 preamp slot did have a fairly well known crosstalk problem between left and right and you could see it come up on the Dolby level meters when applying slit loss. It would break into ringing if boosted enough. I concluded at the time it was in the edge connector wiring or board layout but can't recall the details. Something to watch out for though.

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999


 - posted 09-17-2016 06:36 PM      Profile for Steve Guttag   Email Steve Guttag   Send New Private Message       Edit/Delete Post 
I seem to recall that the CAT108 also had crosstalk issues on the earlier versions. It was fixed before the 108C though.

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Sam D. Chavez
Film God

Posts: 2153
From: Martinez, CA USA
Registered: Aug 2003


 - posted 09-18-2016 12:16 AM      Profile for Sam D. Chavez   Author's Homepage     Send New Private Message       Edit/Delete Post 
Actually the 108C was the fix for crosstalk. I think it the crosstalk was on projector 2.

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999


 - posted 09-18-2016 04:35 AM      Profile for Steve Guttag   Email Steve Guttag   Send New Private Message       Edit/Delete Post 
Are you sure? I think the 108-4 had the fix. The 108C added in the ground plane fill, which, I'm sure, improved its performance yet again. But I'd have to dig up the various schematics to prove it (for something that just doesn't matter anymore anyway) but if it was the 108C, then so be it. The 108C was a good preamp for the CP50/200.

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Sam D. Chavez
Film God

Posts: 2153
From: Martinez, CA USA
Registered: Aug 2003


 - posted 09-18-2016 12:04 PM      Profile for Sam D. Chavez   Author's Homepage     Send New Private Message       Edit/Delete Post 
It's true, it really does not matter. As I remember there was some clever little trick like feedback to minimize the inherent crosstalk issue (due to backplane issues) as well as a number of other enhancements on the 108C. But my memory is far from infallible after all this time.

The more important overall point is this the kind "values" Dolby practiced. Going back and fixing and improving circuitry on processors out of production just to get closer to ideal. Privately held companies bearing the owners name get to do this. At its best, Dolby was run as a laboratory that picked the right products and made money. The rest is history.

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999


 - posted 09-19-2016 09:41 AM      Profile for Steve Guttag   Email Steve Guttag   Send New Private Message       Edit/Delete Post 
So I checked anyway. The crosstalk circuit was added for the 108-4 and was implemented 9FEB1982. It was the first revision of the CAT108 that I could find. The "fix" was a form of feedback from P1 right to P2 Left.

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Sam D. Chavez
Film God

Posts: 2153
From: Martinez, CA USA
Registered: Aug 2003


 - posted 09-19-2016 01:51 PM      Profile for Sam D. Chavez   Author's Homepage     Send New Private Message       Edit/Delete Post 
Keep looking. Who you going to believe, me or your lying eyes?

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