The Dolby 740 is a two-channel, dynamics-based processor for emphasizing low-level sonic details in audio programming.
Whether bringing out the subtleties in all aspects of recording, mastering, postproduction, and live performance, or lending character to audio broadcasts, the Dolby® 740 Spectral Processor provides a high level of flexibility in audio processing. Based on the versatile filtering characteristics of Dolby SR noise reduction, this two-channel dynamic processor allows boosting of low-level signals while leaving high-level signals untouched. Like a magnifying glass for sonic details, the Spectral Processor allows you to tailor your sound like never before.
The Dolby 740 processes low-level signals in a side chain, where as much as 20 dB of boost can be added in low-, mid-, and high- frequency bands. The side chain’s signal is then added to the original input signal, resulting in an output with the low-level details boosted, while the high-level signals remain unaffected.
For maximum effectiveness, the threshold below which the processing occurs, the amount of boost in each band, and the crossovers between bands are all user-adjustable. A gentle sliding-band noise reduction circuit providing up to 12 dB of action is also included, to reduce any source noise that the low-level equalization process might have emphasized. Other controls include a stereo link switch and adjustable output level.
The user adjustments described above make it possible to emphasize ambience, lift harmonics, and bring out otherwise inaccessible details—all without compressing or limiting transients, increasing overall level, or disturbing the overall sense of dynamics.
User adjustments for selectively boosting low-level signals allow broadcasters to tailor the sound for their station, whatever the format. It conveys all the detail of the original source material while eliminating the over-processed sound that can fatigue listeners. When used in conjunction with a conventional compressor/limiter, the Spectral Processor adds greater punch, presence, clarity, and loudness to broadcast signals.
Front-Panel Controls and Indicators
Individual for each channel
Sets level at which signals receive most boost; adjustable from 60 to 40 dB below the nominal operating level; five-LED meter array indicates when processor is most active; input clip LED
Three-band filter section Low-to-Mid crossover frequency adjustable from
75 Hz to 1 kHz, center detent at 300 Hz Mid-to-High crossover frequency adjustable from
500 Hz to 8 kHz, center detent at 2 kHz Boost controls for each band; greater than 20 dB
with crossover controls set to their detent positions Three-position EQ switch selects one
of the following modes: In—processing active; main path and side chain added within the unit; Side Chain—side chain signal only, to ease adjustment of the EQ controls or allow external manipulation; Out—all processing bypassed (including Source NR)
Sliding band noise reduction section reduces noise present in the input signal; adjustable 0–12 dB
Selectable; prevent unwanted signals from entering the low-level processing stage
Highpass: 100, 200 Hz Lowpass: 4, 8 kHz Output: Sets overall channel gain; adjustable from –14 to
+6 dB (with processing out). Clip LED will light to
indicate clipping in the output stage.
Switch combines dynamic processor control signals to prevent image-shifting with stereo signals; EQ Crossover and Boost controls remain independent even when processors are linked
Switch on rear of unit selects between High (+4 dBu) and Low (–6 dBu) line-level operation
XLR type connectors, balanced, floating; impedance: 10 kΩ. Maximum Level: High: +24 dBu; Low: +14 dBu
XLR type connectors, balanced, floating; impedance: 20Ω. Maximum Level: +26 dBu balanced, +21 dBu unbalanced (irrespective of the position of the High/Low switch); either leg of the output may be grounded for unbalanced operation with no loss of level
User-selected voltage nominally 100, 120, 220, 240 VAC 36 W approximate
Dimensions and Weight
1-U rackmount: 44 × 483 × 248 mm (1.75 × 19 × 9.76 inches); further 65 mm (2.5 inches) depth required for the XLR connectors
Net: 5.3 kg (11.6 lb) approximate
0° to 40°C (32° to 104°F)
One-year limited, parts and labor; see disclaimer. Specifications subject to change without notice.
Disclaimer of Warranties
Equipment manufactured by Dolby Laboratories is warranted against defects in materials and workmanship for a period of one year from the date of purchase. There are no other express or implied warranties and no warranty of merchantability or fitness for a particular purpose, or of noninfringement of third-party rights (including, but not limited to, copyright and patent rights).
Limitation of Liability
It is understood and agreed that Dolby Laboratories’ liability whether in contract, in tort, under any warranty, in negligence, or otherwise shall not exceed the cost of repair or replacement of the defective components or accused infringing devices, and under no circumstances shall Dolby Laboratories be liable for incidental, special, direct, indirect, or consequential damages (including, but not limited to, damage to software or recorded audio or visual material), cost of defense, or loss of use, revenue, or profit even if Dolby Laboratories or its agents have been advised, orally or in writing, of the possibility of such damages.
Dolby and the double-D symbol are trademarks of Dolby Laboratories.
© 2004 Dolby Laboratories, Inc. All rights reserved. S04/13656/15267 Part No. 91313 Issue 6
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