This is topic 35mm Mag in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Josh Jones (Member # 447) on 04-30-2000, 02:25 PM:
Does anyone out there know the track layout for 35mm mag? the theatre I work at has two RCA 9010 35mm mag heads that have long been replaced. I'm thinking about hooking one of them up for our "lair" screening room.LittleJosh
Posted by Ari Nordström (Member # 288) on 04-30-2000, 03:12 PM:
The mag sound layout is, in order from the right edge of the film (the optical sound strip side) and inwards:Left ch (1)
Center ch (2)
Surround ch (4)
Right ch (3)
The numbering refers to the numbering scheme in use when mag sound was common, and has nothing to do with the order of appearance...
Posted by Gordon McLeod (Member # 33) on 04-30-2000, 03:24 PM:
tracks 1,2,3,4 are left centre right surround
you need preamps for them and the head impedance can be a bitch to match up on some of the older stuff
Smart still makes a decent 4 channel mag preamp
Posted by Mark Gulbrandsen (Member # 72) on 04-30-2000, 04:15 PM:
Hey Josh,
If you do hook one up be sure to get a new timming belt for it. It links the two sprockets together and the old one usually takes a bad set from sitting around all these years. You'll have lots of wow in your playback. After use if you don't plan on using it for a while remove the belt and leave it in a visible spot for the next operator to install back in.
Posted by Steve Guttag (Member # 268) on 04-30-2000, 04:34 PM:
Jeez Gord....SMART still makes "a" pre-amp for 4-track...certainly cost effective (read, cheap) The SMP-435...it no longer has the dual 12KHz filter of the SMP-430.Dolby's CAT 92C preamp cards also work REALLY well.
Lastly, Panastereo's NEW CSP-4600 accomodates 4-track magnetic 35mm including decoding the 12KHz control signal.
Steve
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"Old projectionists never die, they just changeover!"
Posted by Gordon McLeod (Member # 33) on 04-30-2000, 05:51 PM:
Steve I get the feeling that budget will be the main consideration and there are many of the older 4 track smarts kicking around used with the 12K filter and they did a more than acceptable job on 35mm mag maybe not the best for 70 though
I have often hooked up DBX 3Bx units to the output of the 4 track to quiet them down from the hiss build up
Posted by Steve Guttag (Member # 268) on 04-30-2000, 07:23 PM:
>>"they did a more than acceptable job on 35mm mag"<<Provably false.
But I agree with you that in this situation that it is viable solution that should be considered.
Another noise solution is DNR. Teccon incorporated it on their preamps.
Steve
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"Old projectionists never die, they just changeover!"
Posted by Josh Jones (Member # 447) on 04-30-2000, 08:03 PM:
The timing belt on the head was holding the shape it was in for the last 20 years. I ran some test film loops to figure out how to thread it. Just like dave(My manager, long time projectionist)told me, the ilers were fluttering like crazy. as for preamps, I thought about building them from scratch.
Impedance matching, I now know, could be a problem.LittleJosh
Posted by Steve Guttag (Member # 268) on 04-30-2000, 08:12 PM:
Building the preamps from scratch seems like needless work...unless that sort of thing is your hobby.Gord is right in that there are preamps out there (SMART or otherwise) that could be had cheap (or even free) that will do the trick well enough.
Depending on your print condition, one of your biggest problems will be print shrinkage...see if the picture will even be watchable...I have seen many a 4-track print (old and shrunk) that wouldn't sit still on the intermittent sprocket or film gate.
Steve
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"Old projectionists never die, they just changeover!"
Posted by Mark Gulbrandsen (Member # 72) on 05-01-2000, 06:26 AM:
Another route would be to get the small modules from Oampamp Labs in Hollywood. These are high quality small octal plug in modules and are very inexpensive. There are schematics in the Oampamp Labs info for building the preamp. Also Gord/Steve, The Smart mag preamps are the quietest of the lot that you can buy. Disney uses them extensively all over the place, however they are designed and will eq peoperly only with a Teccon Head. Unfortunately these are no longer around. The 92C would be my choice in this case.
Mark
Posted by Sean Weitzel (Member # 244) on 05-01-2000, 08:13 AM:
What about gutting a pair of old cassette decks for preamps? Just run shielded wires from each head to the spots on the deck's boards for each channel. If you could find a cheap or broken 4 track cassette or small 4 track reel to reel deck, then you'd only need one.. and you would have a built in power supply. -sean
Posted by Mark Gulbrandsen (Member # 72) on 05-01-2000, 09:22 AM:
The tape preamps would have the wrong time constant for proper eq'ing. Propbably not even close. There are alot of things to take into consideration such as head impedance, gap width,linear speed, etc. The ompamp thing works well though. I know someone that has done it before. Also note that the Dolby CAT92 preamp cards probably won't work well either as they are really meant for low impedance heads. If you crank the gain up too much and apply too much hf eq they can oscillate, possibly leading to disastrous results. The 92C cards work quite well with either high or low impedance though.
Mark
Mark
Posted by Josh Jones (Member # 447) on 05-01-2000, 08:00 PM:
Wait just a minute,
In the storage room of the theatre, There was a rack chassis with four little modules each having two tubes and an a shielded transformer. could those be preamps?Josh
Posted by Steve Guttag (Member # 268) on 05-01-2000, 08:42 PM:
Mark,I have tried the SMP-435 with Teccon heads (your's even on your two-strip Centurys) and the EQ was REALLY wanting.
I think we have a couple of either SMP-430s or 435s kicking around somewhere though.
For the best overall, the Cat. 92C is very tough to beat.
Steve
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"Old projectionists never die, they just changeover!"
Posted by John Eickhof (Member # 323) on 05-01-2000, 10:09 PM:
Yes, those are the pre-amps...if you email me a model number off each chassis, Ill send you schematics. The only repairs before you hot them up should be replacing all the capacitors with new ones, also, there should be a power supply in that cabinet for these, send me some numbers and I should be able to help! John
Posted by Josh Jones (Member # 447) on 05-01-2000, 10:53 PM:
John,You might have to wait till later this week.
I only work weekends(granted there's not a track meet), but I'll get those numbers to you .
Thanks
Posted by Bryan Redemske (Member # 354) on 05-02-2000, 07:48 AM:
umm...what's a 35mm mag? i have no clue and probably have never seen one. so, if someone could explain or show me a picture that'd be cool.
Posted by Josh Jones (Member # 447) on 05-02-2000, 08:17 AM:
Bryan,Mag is short for magnetic recording. It was the first form of surround sound with all channels discrete on the film. And until recently, it was the only soundtrack on 70mm film. basically, four strips of magnetic tape were glued somehow onto the film. 35mm film can hold 4 tracks of audio, but 70mm can hold 6. I'll try and find a picture for you,
Josh
Posted by John Pytlak (Member # 331) on 05-02-2000, 08:18 AM:
Bryan:Check out the early history of "Scope", which included 4-track magnetic striped prints, on Marty Hart's "American WideScreen Museum" website:
http://www.simplecom.net/widefilm/widescreen/wingcs1.htm
http://www.simplecom.net/widefilm/widescreen/cinemascoperef.htm
The main site entry link is:
http://www.simplecom.net/widefilm/
IMHO, Marty's site is one of the most facinating and comprehensive sites about motion picture technology on the web. 
------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com
Posted by Bryan Redemske (Member # 354) on 05-02-2000, 08:46 AM:
i see...i read about that in a big Dolby 'history of sound' thing we have at our theatre. i see how it works now though. thanks!
Posted by Mark Gulbrandsen (Member # 72) on 05-02-2000, 01:00 PM:
I agree with you on the SMP 435 mag eq. It is very wanting, but for dailies playback of voice they work great and they are very quiet. All the sound mixers that I have worked with love the playback out of them. Don't ask me which Teccon they were designed around?????? Thats what Norm told me though. Also.....they WILL NOT work at all with high impedance heads. The eq does not even get close.
Any comments Gord....you seem to be a big fan of these preamps.
Mark
Posted by Gordon McLeod (Member # 33) on 05-02-2000, 04:44 PM:
I wouldn't say a great fan but for there price and the limited use they will get they did a very good job. I have a pair of them set up with my Motiographs and have really had no complaints especially considering that there has never been any real eq standards for the older 4 track prints the only Pink noise I ever saw was what was printed for yentl
The smarts were very quiet and had no problem eq'ng for older 50-60's mag prints. They don't eq that well around some of the 70 prints and I have usually put it down to imopedance mismach. The transformers are strappable to change that as I have seen them used on a bunch of MTM dubbers.
Also Ultra Stereo makes a very good mag preamp in both a ten unit version like dolby's and also a single card 4 track for the older CS processorsIf money is no object then I would go for the presetable Inovonics units
Posted by Oscar Neundorfer (Member # 458) on 05-02-2000, 06:57 PM:
Hello to all,I just couldn't stand it any longer, so I finally registered on the Film-Tech forum after reading and enjoying it so very much. There is only so much time in a day, and finding time to read, much less respond, is difficult.
I will go out on a limb here and TRY to remember a bit about the SMP435 EQ. As I recall, the original 435 only had 2 eq adjustments, and when Indiana Jones and the Temple of Doom (I think it was)came out in 70 mag, the eq standards were changed somehow. I don't recall the details. This was back in 1985 I think or somewhere around then. We modified the eq circuits and added a third adjustment.
I recall running pink noise film on Teccon 70 mag heads and we were able to get pretty darn good response for Indiana Jones. I don't recall exactly what the response was, but it seems like it was reasonably flat up to 16kHz or so, maybe plus/minus 2 or 3 db. Not perfect by any stretch, but certainly not bad.
We had this set up at the Belle Meade theatre in Nashville, and it sounded fantastic. Clean, smooth, and quiet!
The old 435's may not have been the best preamps money could buy, but for the price they offered a great value, and we sold a great number of them.
Regarding high Z heads, they were not suitable.
Thanks for letting me join in here!
------------------
Oscar Neundorfer
Chief Engineer
SMART Devices, Inc.
oscar@smartdev.com
Posted by Mark Gulbrandsen (Member # 72) on 05-03-2000, 08:57 AM:
Hi Oscar...how the heck are you and welcome to this wonderful site.
I have used them many times on a double system projector that I build and have had poor luck with the LF response. Seems to roll off several db below about 180 hz or so. These units all have the third adjustment but I wonder if the head impedance on the single stripe teccons are way different. I seem to remember them telling me that is was very similar though.
This has not been a problem at all as we only playback voice for the most part.
Any ideas why this would be so different??
Mark
Posted by Josh Jones (Member # 447) on 05-07-2000, 11:21 AM:
OK, here's the numbers i pulled off the preamps: the preamps MI-9362, Powersupply
MI-9519, and the chassis MI-9269.does someone have the schematics for these?
Josh
Posted by John Walsh (Member # 168) on 05-07-2000, 12:56 PM:
That's old RCA stuff. You will not be able to get any schematics from RCA, that's for sure. I tried in 1980 and even then got nowhere.
Posted by Scott Norwood (Member # 30) on 05-07-2000, 01:19 PM:
With any luck, someone here will have the RCA documentation on these preamps and will hopefully send it to Brad to scan and add to the manuals section. I sent him the Simplex/Altec Magsound Package documentation (circa 1955), which is surprisingly good...
Posted by Per Hauberg (Member # 529) on 07-11-2000, 06:26 PM:
35 mag - Gosh, that's some days ago, and the prints were not many at this end of the world. A single print of "Patton" mag/opt got my special attention: the 12Khz tone was hearable in auditorium - not only by me, but in all cinemas, i saw it in. -Anyone know, if that was normal a printing failure on that particular one...?"River Kwai" was here in a 3-track-only mag print (no surround). Was that the normal version, or did it excist in regular 4-track ? -And if, - then why this amputated one ??
-Likewise: Both danish prints of "JCSuperstar" were without surround, -but those 3 remaining tracks sounded damned well.
Anyone tryed the Dolby Stereo reissue prints (late 80'es) of this one - were they any good...??
Last new 35 mag prints in Denmark were 1941, Star Wars 1 and Fantasia reissue, but even before those, i guess we were often cheeted, running mono prints only from films, running elsewhere with great sound. -Wasn't the mag sound quite used in US and Britain, even during the seventies...??
Posted by Per Hauberg (Member # 529) on 07-22-2000, 03:35 PM:
B I G S I G H ! !I do use both soap and toothpaste, but i'd got to admit, i'd never heard of Film Guard before getting into this great forum, and therefore, i do not use that - yet (!)
Maybe that why i feel, nobody wants to answer my questions on this topic...
Very sad, very alone in the booth, very uninformed 
Per
Posted by Brad Miller (Member # 2) on 07-22-2000, 04:41 PM:
Whether you use a product or not has nothing to do with whether people will answer your questions. If you pose a question and no one has the answer, you will not get a response. I'd answer your questions myself, but I don't know the answers either.
Posted by Per Hauberg (Member # 529) on 07-22-2000, 06:35 PM:
Hi, Brad !OK - who else should have the right answer for that one... -Just imagined, after surfing those many topic's, that this bunch of old pro's knew everything.
At my end of the world, btw, we still suffer by the commercial about not being spoken to, unless You use Colgate toothpaste. 
Well - both toothpaste and the filmstars' favourite beauty soap is available in Denmark - Film Guard is not, -and even if it would help me getting an answer to my dull questions about mag sound, i still would like to try that miracle of Yours. Will Film-Tech manage overseas sales Yourself ?
How, to whom and how much for the first try ? - and how expensive is the pad equipment (35/70) for the projector..?
Greetings / Per
Posted by Per Hauberg (Member # 529) on 07-22-2000, 06:39 PM:
brad-"even if it would NOT help me"
it should say...
sorry about that one
per
Posted by Martin Frandsen (Member # 74) on 07-23-2000, 07:45 AM:
Per, to order (international) call/ or fax Cinema Equipment Sales of California, they take care of supplies of FG to us at the far end of the world For more information click on ''Film-Cleaning'' in the menu-bar, then click ''dealers'', scroll down to ''International-dealer'', hope this helps! 
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It's the new small talk. You do it so awfully well! - My Fair Lady
Posted by Ari Nordström (Member # 288) on 07-23-2000, 01:17 PM:
Per,Regarding the 12kHz tone heard in 35mm mag prints of "Patton", I understand this was not entirely uncommon. Speaking to old projectionists, many confirm this and speak of the problem as one of the quirks of that particular system. Our tech also confirms this.
I've never run "Patton" in 35mm mag, but I did hear a 12 kHz tone when screening a reel of "Fiddler on the Roof" (if memory serves).
Posted by Oscar Neundorfer (Member # 458) on 07-23-2000, 02:07 PM:
The 12 kHz tone was a form of rudimentary noise reduction. It was used on the surround track to turn the surround channel on and off. The presence of the tone indicated surround material, and a tone detector would sense the tone and turn on the surround channel. The tone was normally filtered out so you did not hear it. Since the mag stripe on the surround track was narrower than the other tracks, it was noisier. Therefore this method would only turn surrounds on when material was present on the surround track to help mask the noise.The new Panastereo 70mm system handles this format nicely, and you don't hear the tone at all.
------------------
Oscar Neundorfer
Chief Engineer
SMART Devices, Inc.
oscar@smartdev.com
Posted by Ari Nordström (Member # 288) on 07-24-2000, 01:34 PM:
I should add to my previous post on the subject that we did, at the time, have the equipment necessary to handle 35 mag sound with the 12 kHz tone. It was rarely put into use, though.The CP500 we have now can't handle this format, can it?
Posted by Ari Nordström (Member # 288) on 07-24-2000, 01:38 PM:
I'm really clicking "Submit Reply" too fast today. Please add "Dolby MPU" to "CP500" in the above post... 
Posted by John Walsh (Member # 168) on 07-24-2000, 02:10 PM:
The Dolby MPU did have a card slot specifically for a 12khz switch card. They probably made a few, but I don't know if you could get any (new) from them now.
Posted by John Eickhof (Member # 323) on 07-24-2000, 06:55 PM:
It isn't difficult to build a passive notch filter to eliminate the 12K, I have built many with excellent results and less than .5db insert loss. (at pre-amp line level)
Email me if you want a schematic and parts list FREE!