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Summary of Contents for Inovonics 261
- Page 1 OPERATING AND MAINTENANCE INSTRUCTION MANUAL MODEL 261 DIGITAL UTILITY AUDIO PROCESSOR interstage Phistersvej 31, 2900 Hellerup, Danmark Telefon 3946 0000, fax 3946 0040 www.interstage.dk - pro audio with a smile...
- Page 3 USER S RECORD Model 261 Serial No. ____________ Date Purchased __________________ Warranty Card Mailed? OPERATING AND MAINTENANCE INSTRUCTION MANUAL MODEL 261 DIGITAL UTILITY AUDIO PROCESSOR Rev. 2 March, 2008 (HF Limiter Addition) 1305 Fair Avenue Santa Cruz, CA 95060 TEL: (831) 458-0552 FAX: (831) 458-0554 Visit our Website: www.inovon.com...
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Page 5: Table Of Contents
PROCESSING FUNCTIONS DISCUSSED AND ILLUSTRATED......Status Screen Gated AGC AGC Response Gating Defined and the GATE Indicators AGC Rate (Speed) Maximum AGC Gain AGC Range Alarm The Dynamics of Model 261 Processing The Compression Platform The Limit-Only Mode Limiter Overload Limit and Compress... - Page 6 THE 261 AS AN FM AIRCHAIN PROCESSOR ............The Independent High Frequency Limiter Flat or Pre-Emphasized Output Section IV - CIRCUIT DESCRIPTIONS INTRODUCTION ..................... Component Annotation ANALOG INPUTS AND OUTPUTS ................Analog Line Input Analog Line Output DIGITAL INPUTS AND OUTPUTS ................
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Page 7: Section I - Introduction
The 261 is set up and controlled by navigating a menu with a simple series of pushbuttons. A rear-panel switch may be used to lock-out the front-panel selector buttons to protect processor setup. -
Page 8: Model 261 Technical Specifications
MODEL 261 TECHNICAL SPECIFICATIONS Frequency Response: AGC Function: ±0.25dB, 20Hz-20kHz at 44.1kHz Unobtrusive, peak-and-average- and 48kHz sampling rates; weighted correction for long-term ±0.25dB, 20Hz-15kHz at 32kHz input level variations; ±15dB cap- sampling rate. ture range. Noise: Compressor/Limiter: Digital Mode: Better than 120dB... -
Page 9: Block Diagram
BLOCK DIAGRAM Figure 1, below, is a simplified Block Diagram of the Model 261, shown as an analog equivalent of the digital audio processing ar- chitecture. A full set of schematic diagrams appears in the Appen- dix, Section V. Figure 1 - Block Diagram, Model 261 Digital Utility Processor... -
Page 10: Section Ii - Installation
Requirement screws with plastic washers to protect the painted finish around the mounting holes. Consuming less power than a fish-tank air pump, the 261 itself gen- Heat Dissipation erates negligible heat. The unit is specified for operation within an ambient temperature range extending from freezing to 120°F/50°C. -
Page 11: Radio Frequency Interference (R F I)
BLUE = AC NEUTRAL GRN/YEL = EARTH GROUND RADIO FREQUENCY INTERFERENCE (R F I) Although the Model 261 is expected to be installed in the vicinity of Location high-power radio or TV transmitters, please practice reasonable care and common sense in locating the unit away from abnormally high RF fields. -
Page 12: Line Input And Range Selection
The three push-on positions are marked: 10, 0 and +10. Choose the position that is closest to the nominal, zero-VU program line level that is connected to the analog input of the Model 261. If the line level is +4dBm, select the position. -
Page 13: Line Outputs
Digital Output connector delivering an electronically-balanced (transformerless) digital signal. When the 261 is fed with a digital input, this output will assume the same sampling rate. When the 261 is fed left-and- right analog inputs, the output sampling rate is selected by the front-panel menu. -
Page 14: Self-Calibration Utility
SELF-CALIBRATION UTILITY The 261 incorporates a self-calibration routine that automatically compensates for inevitable DC offsets in the D-to-A converter. Nor- mally this routine is performed at the factory and does not have to be repeated on a routine basis. However, if either the DSP board or... -
Page 15: Section Iii - Setup And Operation
261 will return to an as left condition following a power interruption. Because the t and u buttons make actual (and audible) changes in... -
Page 16: Output Sampling Rate
The 261 monitors the AGC-corrected program level through a fre- quency-weighting filter that favors legitimate speech and music fre- quencies. When the program level falls approximately 26dB below nominal for a period of 10 consecutive seconds, the 261 will give the alarm shown in the illustration. Concurrent... -
Page 17: Setting Levels
INPUT gain: COMPRESSION/LIMITING when AGC is not used. The Model 261 has bodacious internal headroom in both the analog Input Overload and the digital domains. There are two alarms, however, that moni- Alarms tor program waveform excursions to alert the operator should in- ternal levels reach about 95% of digital full-scale. -
Page 18: Processing Functions Discussed And Illustrated
This primary alarm has an integrated peak response to program sig- nal overloads, allowing the occasional transient to slip through. However, a secondary indicator, marked OVERLOAD (arrow) has in- stantaneous peak response. This secondary flasher is held for a suf- ficient period to make even the briefest overload visible to the opera- tor. - Page 19 The AGC has a resting value at the 0dB point on the AGC GAIN scale. A proper adjustment of Model 261 input gain causes the AGC to hover around the 0dB mark most of the time that the AGC is op- erating.
- Page 20 FAST Classical and jazz music may suffer this risk as well. AGC setting is always useful when setting up the 261, al- FAST lowing to be set more quickly. AGC should probably be...
- Page 21 1:1 input vs. output relationship would take a different slope; maybe 1.5:1, 2:1 or even steeper. But com- pression, as offered by the 261 and many other fine Inovonics prod- ucts, means just that: compression of the program dynamic range.
- Page 22 The independent high frequency, pre-emphasis-protection limiter is a separate function and is discussed on Page 20. Although the 261 s limiter can be used entirely by itself (with AGC The Limit-Only and Compression turned off), we recommend using AGC ahead of Mode the limiter.
- Page 23 The combination of all three processing functions ensures a certain consistency to the audio program. This illustration shows how the 261 might appear in operation as a general-purpose leveler for loudness normalization.
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Page 24: The 261 As An Fm Airchain Processor
50µs or 75µs pre-emphasis transmission curves: When either characteristic chosen, another programming option be- comes available. With the HF limiter engaged, the output of the 261 may be set to Flat or Pre- have either a flat or a pre-emphasized output characteristic. This is... - Page 25 CAUTION: Be aware that double pre-emphasis will result if the 261 is set as shown above, and the stereo generator or FM exciter imparts transmission pre-emphasis as well. This is a condition to be avoided like the proverbial plague.
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Page 26: Section Iv - Circuit Descriptions
Section IV CIRCUIT DESCRIPTIONS INTRODUCTION This Section details the circuitry of the Inovonics Model 261 Digital Utility Audio Processor. Circuit descriptions refer to the four pages of Schematic Diagrams contained in the Appendix, Section V. Schematics for the 261 may appear to have component reference Component designations assigned in a haphazard manner. -
Page 27: Digital Inputs And Outputs
35 of J9. The vari- ous sections of IC6 deliver a quasi-balanced AES/EBU digital output to the connector of the same name on the rear panel of the 261. ALARM TALLIES The DSP chip, IC2, directly drives three transistors, Q1, Q2 and Q3. -
Page 28: Program And Settings Memory
Omitting a communi- cations port in the Model 261 has greatly simplified the design, and was judged not to pose a compromise in an otherwise uncomplicated... -
Page 29: Section V - Appendix
Section V APPENDIX This section of the Model 261 Manual con- tains Parts Listings, Schematic Diagrams and an explanation of Inovonics Generous and Liberal Warranty Policy. -
Page 30: Explanation Of Parts Listings
PARTS LIST EXPLANATION OF PARTS LISTINGS This section contains listings of component parts used in the Inovon- ics 261 Digital Utility Processor. Not all components are listed by schematic reference designation; those that are considered generic may have qualification notations, however. - Page 31 Transistor, NPN; (open) 2N3904 Except at noted by reference designation, all resistors used in the 261 are the value specified on the schematic, qualified as follows: a: Resistors with values carried to decimal places implying a 1% tolerance (example: 232, 3.01k, 10.0k, 301k) are ¼-watt, 1% metal film type.
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Page 32: Sources For Component Parts
Inovonics strives to maintain factory stock of the parts used in products that we manufacture. A good many of the components in the Model 261 are generic and may be obtained from a wide variety of sources. A few parts may be more-or-less proprietary. -
Page 37: Inovonics Warranty
CONDITIONS OF WARRANTY: The following terms apply unless amended in writing by Inovonics, Inc. A. The Warranty Registration Card supplied with this product must be completed and returned to Inovonics within 10 days of deliv- ery. B. This Warranty applies only to products sold as new.
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