USL JSD-80 Manual - Manual (Page 25)

USL, Inc. JSD-80 Instruction Manual Page 25 3rd Edition. February, 2006
will be necessary to reposition the
fi lm guide roller and realign the solar
cell, so that both the 50% and 100%
modulated tones match from channel
to channel. When this fi ne alignment
is not done, loud sounds (above 50%
modulation) will be distorted and will
leak into the surround channels.
8. Using the built-in Slit EQ Analyzer,
run a pink noise test fi lm (Cat 69P or
equivalent). Adjust the focus of the
soundhead optics for the best high
frequency response on the analyzer
(see below). At the same time, adjust
the azimuth for the thinnest display
on the oscilloscope. The focus and azi-
muth adjustments interact, so it will be
necessary to keep adjusting both until
the best combination is achieved.
9. Using the built-in SLIT EQ Analyzer
adjust the SLIT EQ slider until the re-
sponse is fl at to 12 kHz +/- 1 dB.
8.3 Sum and Difference mode.
No Oscilloscope required.
When running a Cat 69P Pink Noise loop on
the projector, precisely adjust the left and
right projector gains so the red and green
lines on the slit analyzer overlap.
Click “Normal” on the Slit EQ Analyzer. The
button designation changes to “Sum & Diff.”
Adjust the projector sound head so the two
graphs are roughly parallel.
The top graph is controlled primarily by
the focus of the reader. The bottom graph
is controlled primarily by the azimuth.
First, the focus must be adjusted to achieve
the best high frequency response for the
top curve.
Most likely, the bottom graph will rise
quickly at high frequencies. Carefully rotate
the sound lens or reader until the curve is
horizontal.
Note: It is a bit of a juggling act to keep
rotating the reader and focusing it to
achieve the best high frequency response
on the top graph and the most horizontal
response on the bottom graph.