Key Features - OPTIMOD-FM 8600Si Audio Processor
User Friendly Interface
An LCD and full-time LED meters make setup, adjustment and programming of OPTIMOD-FM easy - you can always see the metering while you are adjusting the processor. Navigation is by dedicated buttons, soft buttons (whose functions are context-sensitive), and a large rotary knob. The LED’s show all metering functions of the processing structure (Two-Band or Five-Band) in use.
Absolute Control of Peak Modulation
The 8600Si provides universal transmitter protection and audio processing for FM broadcast. It can be configured to interface ideally with any commonly found transmission system in the world, analog or digital.
The 8600Si provides pre-emphasis limiting for the internationally used pre- emphasis curves of 50μs and 75μs. Compared to its predecessor, its new clipping/pre-emphasis control technology preserves 2.5 to 3 dB more frequency energy while significantly reducing audible clipping distortion at all frequencies. This produces a clean, open sound whose subjective brightness more closely matches the original program.
The 8600Si achieves extremely tight peak control at all its outputs - analog, AES3 (for both the analog FM and HD channels), and composite baseband.
The stereo encoder has two outputs with independent level controls, each capable of driving 75Ω in parallel with 47,000pF, (100ft / 30m of coaxial cable).
By integrating the stereo encoder with the audio processing, the 8600Si eliminates the overshoot problems that waste valuable modulation in traditional external encoders.
The 8600Si prevents aliasing distortion in subsequent stereo encoders or trans- mission links by providing bandwidth limiting and overshoot compensated 15 kHz low-pass filters ahead of the 8600S’s audio outputs and stereo encoder.
The 8600Si has an internal, DSP-based stereo encoder (with a patented “half-cosine interpolation” composite limiter operating at 512 kHz sample rate) to generate the pilot tone stereo baseband signal and control its peak level. The composite limiter is a unique, “you can only do this in DSP” process that beats composite clippers by preserving stereo imaging while fully protecting the stereo pilot tone, RDS/RBDS, and subcarriers. The stereo encoder’s stereo sub-channel modulator can operate in normal double sideband mode and in an experimental compatible single sideband mode that is offered to enable users to compare and assess the two modes.
The Digital Radio and analog radio processing chains offer ITU-R BS.1770-3+ Loudness Meters and Safety Limiters for use in countries that enforce a BS.1770 loudness limit on digital and/or analog radio broadcasts.
The 8600Si implements “true peak” control in its HD processing chain by oversampling the HD peak limiter’s sidechain at 256 kHz. This allows the 8600 to prevent clipping in a playback device’s analog signal pathby predicting and controlling the analog peak level following the playback device’s reconstruction filter to an accuracy of better than 0.5 dB. For typical program material, accuracy is 0.2 dB.
Without true peak control, analog clipping can occur even if all peak values of the digital samples are below 0 dBFS. This phenomenon has also been termed “0 dBFS+.” Thanks to true peak control, sample rate conversion, unless it removes high frequency program energy or introduces group delay distortion, cannot cause sample peaks to increase more than 0.5 dB. For example, sample rate conversion from 48 kHz to 44.1 kHz is highly unlikely to cause sample peak clipping in the 44.1 kHz audio data.
A built-in RDS/RBDS encoder supports the most important RDS features and can be associated with processing presets so that mixed-format stations can automatically update the “program type” field to complement the programming by recalling a audio processing preset for a given program type.
OPTIMOD-FM 8600Si is supplied with analog and AES3 digital inputs and outputs. The digital input and the two digital outputs are equipped with samplerate converters and can operate at 32 kHz, 44.1 kHz, 48 kHz, 88.1 kHz, and 96 kHz sample rates. The pre-emphasis status and output levels are separately adjustable for the analog and digital outputs. Each output can emit the analog FM processed signal, the analog FM processed signal with diversity delay applied, the digital radio processed signal, or the low-delay monitor signal.
A loop-through connection is provided to enable a ratings encoder (such as Arbitron®) to be inserted between the output of the audio processing and the input to the stereo encoder. . In “ratings encoder loop-through mode,” the second digital output drives the ratings encoder from the output of the FM processing.
Failsafe switching detects loss of audio on the primary input, which you can assign to be the analog or digital input. If audio is lost on the primary input, the 8600Si can switch automatically to the secondary input.
The 8600Si has two independent equalizers, multiband compressors, and peak limiters for the FM analog and digital media processing channels, allowing you to separately optimize the processing for each.
An AES11 sync input allows you to synchronize the output sample rate of either (or both) AES3 outputs to this input. You can also synchronize the outputs to the AES3 digital input or to 8600Si’s internal clock. The sync source of each AES3 output is independently selectable.
A defeatable diversity delay can delay the FM analog processing output up to 16.2 seconds. Delay can be trimmed in intervals of one sample of 64 kHz to match the analog and digital paths in the HD Radio system, eliminating the need to use the delay built into the HD Radio exciter and permitting the 8600Si’s internal stereo encoder and composite limiter to drive the analog FM exciter. Each output (Analog, Digital 1, Digital 2, Composite) can be independently configured to emit the delayed or non delayed signal.
The analog inputs are transformerless, balanced 10kΩ instrumentation- amplifier circuits. The analog outputs are transformerless balanced and floating (with 50Ω impedance) to ensure highest transparency and accurate pulse response.
The 8600Si has two independent composite baseband outputs with digitally programmable output levels. Robust line drivers enable them to drive 100 feet of RG-59 coaxial cable without audible performance degradation.
The 8600Si’s two subcarrier inputs are mixed with the output of the 8600S’s stereo encoder before application to the composite output connectors. One in- put can be re-jumpered to provide a 19 kHz pilot reference output. Both inputs have internal level trims to accommodate subcarrier generators with output levels as low as 220 mV.
The 8600Si precisely controls the audio bandwidth of its analog FM processing to 16.5 kHz. This prevents significant overshoots in uncompressed digital links operating at a 44.1 kHz-sample rate or higher and prevents interference to the pilot tone and RDS (or RBDS) subcarrier. The bandwidth of the 8600Si’s digital radio output is adjustable in 1 kHz increments between 15 kHz and 20 kHz.
The 8600Si has a defeatable multiplex power limiter that controls the multiplex power to ITU-R BS412 standards. An adjustable threshold allows a station to achieve maximum legal multiplex power even if the downstream transmission system introduces peak overshoots into the 8600S-processed signal. Because this limiter closes a feedback loop around the audio processing, it allows the user to adjust the processor’s subjective setup controls freely without violating BS412 limits, regardless of program material. The multiplex power limiter acts on all outputs (not just the composite output). In its most common configuration, it reduces clipper drive when it reduces power, simultaneously reducing clipping distortion. However, to accommodate customers who wish to use heavier clipping to achieve a certain sound, the MPX power controller can be configured to reduce gain after the clippers.
All input, output, and power connections are rigorously RFI-suppressed to Orban’s traditional exacting standards, ensuring trouble-free installation.
The 8600Si is designed and certified to meet all applicable international safety and emissions standards.
Adaptability Through Multiple Audio Processing Structures
A processing structure is a program that operates as a complete audio processing system. The 8600Si realizes its processing structures as a series of high- speed mathematical computations made by Digital Signal Processing (DSP) chips.
The 8600Si features six processing structures. Four of these are the same as Optimod-FM 8500: Five-Band (or “Multiband”) for a consistent, “processed” sound with 17 ms delay (typical), free from undesirable side effects, Low-Latency Five-Band (12 ms delay), Ultra-Low-Latency Five-Band (3.7 ms delay), and Two-Band (17 or 22 ms delay) for a transparent sound that preserves the frequency balance of the original program material. A special Two-Band preset creates a no-compromise “Protect” function that is functionally similar to the “Protect” structures in earlier Orban digital processors.
The 8600Si’s two “MX” structures (five-band and two-band) are similar to their 8500 counterparts except that they use the 8600S’s new peak limiting technology to decrease distortion while achieving substantial improvements in transient punch and high frequency clarity. This advanced technology requires more input-to-output delay than the older structures, so it is impractical for talent to monitor these structures off-air with headphones The 8600Si offers a special low-delay monitor output for this purpose.
The 8600Si can increase the density and loudness of the program material by multiband compression, limiting, and clipping—improving the consistency of the station’s sound and increasing loudness and definition remarkably, without producing unpleasant side effects.
The 8600Si rides gain over an adjustable range of up to 25 dB, compressing dynamic range and compensating for both operator gain-riding errors and gain in- consistencies in automated systems.
The 8600Si’s Two-Band processing structures can be made phase-linear to maximize audible transparency.
The 8600Si can be remote-controlled by 5-12V pulses applied to eight programmable, optically-isolated “general-purpose interface” (GPI) ports available at the REMOTE INTERFACE connector on the rear panel.
8600Si PC Remote software is a graphical application that runs under Windows 2000/XP/Vista/7/8/8.1 and 10. It communicates with a given 8600S via TCP/IP over modem, direct serial, and Ethernet connections. You can configure PC Remote to switch between many 8600Sis via a convenient organizer that supports giving any 8600Si an alias and grouping multiple 8600Sis into folders. Clicking a 8600Si’s icon causes PC Remote to connect to that 8600Si through an Ethernet network, or initiates a Windows Dial-Up or Direct Cable Connection if appropriate. The PC Remote software allows the user to access all 8600Si features (including advanced controls not available from the 8600Si’s front panel), and allows the user to archive and restore presets, automation lists, and system setups (containing I/O levels, digital word lengths, GPI functional assignments, etc.).
The 8600Si contains a versatile real-time clock, which allows automation of various events (including recalling presets) at pre-programmed times. The clock can be set automatically from an Internet timeserver.
A Bypass Test Mode can be invoked locally, by remote control (from either the 8600Si’s GPI port or the 8600Si PC Remote application), or by automation to permit broadcast system test and alignment or “proof of performance” tests.
Silence alarm and digital audio fault tally outputs are available.
The 8600Si contains a built-in line-up tone generator, facilitating quick and accurate level setting in any system.
The 8600Si's software can be upgraded by running Orban-supplied downloadable upgrade software on a PC. The upgrade can occur remotely through the 8600Si’s Ethernet port or serial port (connected to an external modem), or locally (by connecting a Windows® computer to the 8600Si’s serial port through the supplied null modem cable).