Film-Tech Forum ARCHIVE: DTS Speed/Pitch gone crazy!

This is topic DTS Speed/Pitch gone crazy! in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Matt Close (Member # 996) on 01-02-2007, 12:27 AM:

Guys, has anyone had their DTS6D suddenly decide to vary the pitch up and down while playing????? It keeps pretty much in sync with the picture, but it 'sounds' like I am sitting in the booth winding a record by hand! [Roll Eyes]

It has done this two days in a row now .... I can't be sure if it is only with certain movies, or if it is after 'x' hours of warm-up/operation. On both days, Happy Feet has gone through 2 sessions with no dramas but Charlette's Web and Casino Royale have both had this pitch problem. The problem has not happened on our other DTS6D, so I am leaning towards an equipment fault?

Anyone had this happen? ... Any ideas?

Posted by Mike Blakesley (Member # 26) on 01-02-2007, 02:20 AM:

Check the film as it's going from the platter to the DTS reader. If the film is speeding up/slowing down due to not enough tension on the platter rollers, you'll get the wow effect.

Posted by Brad Miller (Member # 2) on 01-02-2007, 04:21 AM:

Actually no...it is if there is a BOUNCE in the payout of the film. Tension has absolutely nothing to do with it. If tension was required, people with SPECO, Strong and other such platters could never run dts because they have virtually zero backtension.

Wobbley rollers or that spring in an AW3 brain are pretty much the culprit here. The same thing can happen when running reel to reel if the feed reel clutch has issues (even minor).

Posted by Monte L Fullmer (Member # 2797) on 01-02-2007, 04:40 AM:

Since I'm "stuck" with STRONG platters, this is how I set my upper feed rollers up for the DTS lacing procedure - to get the film in the tightest "S" configuration so I can have minimal 'bounce' since I don't have any of that back tension on the film as does the Christie AW3(r) platters have on payout.

And with this procedure, I never have any timecode dropouts during playback.

Also, if I get any prints without any DTS timecode, then I can simply bypass the reader by lacing the film just behind that top back roller then straight down to the upper constant speed sprocket.

-Monte

Posted by Brad Miller (Member # 2) on 01-02-2007, 05:40 AM:

Putting a 180 degree wrap around a ball bearing based roller is not going to add eny extra perceiveable tension. The film can still bounce.

Posted by Steve Guttag (Member # 268) on 01-02-2007, 08:46 AM:

What the larger wraps do is take advantage of the static friction in the bearings of the system to act like dampers. While it will not do anything for a lunging type speed variation (bad centerfeed spring for instance)...it will dampen out light speed variations that have less force than the bearing friction. It will also tend to guide the film a bit better.

On a similar topic...with Kinoton projectors...how one orients the double rollers just below the intermittent will have a great affect on the film as it enters the soundhead...one can litterally tune the film so it is smooth entering the soundhead.

Since Brad likes the AA2 so much...look at what sending the film through the "S" bend rollers after the intermittent on a AA2 does for stabilizing the film as it enters the soundhead....almost all of the intermittent movement of the film is gone before the pinch roller gets it.

Steve

Posted by Monte L Fullmer (Member # 2797) on 01-02-2007, 08:49 PM:

Course you know about the slightly complex roller system that the old Cinemecanicca V4E's had after the film left the intermittent sprocket to head to that split scanner drum - and can we pick on the V8r's as well with this - to smooth out any film ripple before entering the scanner drum area..?

Posted by Gordon McLeod (Member # 33) on 01-02-2007, 10:27 PM:

The vic 4 aand Vic10 had the ssame multi rolleer damping system