4-2
4.2
Digital Soundhead Delay Adjustment
On a Dolby Digital print, the digital data is located 6 frames in advance of the analog
soundtrack, and 26 frames in advance of the picture. When the Digital Soundhead is
mounted above the analog soundhead (as with the Cat. No. 700) a delay is necessary to
synchronize the digital soundtrack with the analog track and the picture. In the DA20,
this delay is set by adjusting three middle rotary switches on the Cat. No. 611A Cinema
Processor Interface Card (located between the analog LED and the proj. 1 LED of the C.P.
Status slot in the front panel of the DA20). SW1 (upper), SW2 (center), and SW3 (lower)
select a delay from 016 to 528 film perforations. SW1 selects hundreds of perfs, and has
the largest effect on delay, SW2 sets tens of perfs, and SW3 single perfs. The maximum
settable delay is 528 perfs (about 5.33 seconds). The minimum delay is 16 perfs (about 170
ms) and is set by propagation delays within the DA20 decoding process.
The table below shows representative settings for a variety of common projectors in use:
Dolby External Digital Readers:
Projector
Delay
Projector
Delay
Ballantyne 35mm
247
Christie
250
Century 35mm (SA)
245
Norelco/ Kinoton
Century 35/70 (JJ)
309
AAII (DP70)
283
Cinemaccanica V5
252
Simplex 35mm (XL)
242
Cinemaccanica V8
260
Simplex 35/70
298
Built-in Digital Readers:
Projector
Delay
Projector
Delay
Century w/ Component
Cinemaccanica V5
28
Engineering or Kelmar
20
Simplex w/ Component
Christie
26
Engineering or Kelmar
26
Soundhead delay may be adjusted in either of two ways:
STATIC
1.
Thread a length of Cat. No. 1010 Digital Soundhead alignment test film such that
the “bullet” frame (perf 106) is located in the picture gate, and perf number 26 is
located at the analog soundhead.
2.
With the length threaded through the Cat. No. 700 Digital Soundhead, read the
number of the perforation present in the light path of the Digital Soundhead. Dial
this number into the Cat. No. 611 CP interface card switches SW1, SW2, and SW3.
3.
Verify the accuracy of the setting by running a loop of Cat. No. 1010 test film and
observing that the flash on the screen coincides with the pip in the sound.
