Key Features - OPTIMOD-FM 5500i Audio Processor
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 LEDs show all metering functions of the processing structure (Two-Band or Five-Band) in use.
The 5500i 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.
The 5500i provides pre-emphasis limiting for the two standard pre-emphasis curves of 50μs and 75μs. Its pre-emphasis control is seldom audibly apparent, producing a clean, open sound with subjective brightness matching the original program.
The 5500i achieves extremely tight peak control at all its outputs - analog left/right, AES3 left/right, and composite baseband.
By integrating the stereo encoder with the audio processing, the 5500i eliminates the overshoot problems that waste valuable modulation in traditional external encoders. 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).
The 5500i prevents aliasing distortion in subsequent stereo encoders or transmission links by providing bandwidth-limiting and overshoot-compensated 15 kHz low-pass filters ahead of the 5500i’s audio outputs and stereo encoder.
Anti-aliased clippers running at 256 kHz sample rate prevent any trace of “digital clipper” sound.
The stereo encoder’s stereo subchannel 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 5500i includes analog and AES3 digital inputs and outputs. Both digital input and digital output are equipped with sample-rate converters and can operate at 32 kHz, 44.1 kHz, 48, 88.2, and 96 kHz sample rates. The pre-emphasis status and output levels are separately adjustable for the analog and digital out- puts.
The 5500i 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 5500i includes a full-featured RBS/RBDS generator. The generator supports dynamic PS. It can be controlled via the 5700 presets and an ASCII terminal server that can be connected to automation to support displaying title and artist.
The analog inputs are transformerless, balanced 10kΩ instrumentation- amplifier circuits, and the analog outputs are transformerless balanced, and floating (with 50Ω impedance) to ensure highest transparency and accurate pulse response.
The 5500i 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 5500i has two subcarrier inputs that are mixed with the output of OPTIMOD-FM’s stereo encoder before application to the composite output connectors. One input can be re-jumpered to provide a 19 kHz pilot reference out- put. Rear-panel accessible PC-board-mounted trim pots allow the user to adjust the sensitivities of the two SCA inputs, allowing both inputs to accommodate subcarrier generators with output levels as low as 100 mV p-p.
The 5500i precisely controls the audio bandwidth to 15 kHz. This prevents overshoots in uncompressed digital links operating at a 32 kHz-sample rate and prevents interference to the pilot tone and RDS (or RBDS) subcarrier.
The 5500i has a de-featable 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 5500i-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). It reduces clipper drive when it reduces power, simultaneously reducing clipping distortion. To prevent audible gain pumping, a user-adjustable gain offset control allows the user to minimize the amount of gain control that the controller performs.
The 5500i has a Wordclock/10 MHz Sync Reference Input (called REF IN), which can be used to lock the stereo pilot tone to a high precision external reference like a GPS-based frequency standard. This facilitates using the 5500i in single-frequency network applications.
The 5500i can delay its output by as much as 16 seconds. This delay can be used as the diversity delay in HD RadioTM installations, which allows the 5500i’s stereo encoder (including composite limiter) to be used in an HD Radio installation.
All input, output, and power connections are rigorously RFI-suppressed to Orban’s traditional exacting standards, ensuring trouble-free installation.
The 5500i 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. Only one processing structure can be on-air at a time. OPTIMOD- FM realizes its processing structures as a series of high-speed mathematical computations made by Digital Signal Processing (DSP) chips.
The 5500i features four processing structures: Stand-Alone Stereo Encoder, Optimum Five-Band (or “Multiband”; 15 ms delay) for a consistent, “processed” sound, free from undesirable side effects, Ultra-Low-Latency Five-Band (5 ms delay) for environments where talent monitors live off-air and they object to the delay of Optimum Five-Band, and Two-Band 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 Optimum Five-Band and the Two-Band structures can be switched via a mute-free cross-fade.
Note: Switching to or from the Ultra-Low Latency Five-Band structure causes the audio to mute for about two seconds because the DSP code must be reloaded.
The 5500i can increase the density and loudness of the program material by multiband compression, limiting, and clipping. This improves the consistency of the station’s sound and increasing loudness and definition remarkably, without producing unpleasant side effects.
The 5500i rides gain over an adjustable range of up to 25 dB, compressing dynamic range and compensating for both operator gain-riding errors and gain inconsistencies in automated systems.
The 5500i’s Two-Band processing structure is phase-linear to maximize audible transparency.
The 5500i can import and run any 8300, 8400, or 8500 “LL” (Low-Latency) preset via the 5500i PC Remote application. This means that you can use an 8300, 8400, or 8500 to develop presets for 5500i if you do not use features in the other processors not supported by the 5500i. (If you try to import a preset that uses features unsupported by 5500i, the 5500i will interpret that preset as best it can by using the available 5500i features).
Analog Fallback to Digital control that allows Silence Sense to switch the active input from Analog to Digital if silence is detected in the analog input signal but not on the digital input signal. This function works vice versa as well on both analog and digital AES input. The silence sense parameters apply to both simultaneously and both detectors are available to drive the 5500i's tally outputs and sending SNMP Traps/Alerts.
Silence alarm and digital audio fault tally outputs are available in both audio processing and stand-alone stereo encoder modes.
The 5500i 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.
5500i 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 5500i via TCP/IP over modem, direct serial, and Ethernet connections. You can configure PC Remote to switch between many 5500is via a convenient organizer that supports giving any 5500i an alias and grouping multiple 5500is into folders. Clicking a 5500i’s icon causes PC Remote to connect to that 5500i 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 5500i features (including advanced controls not available from the 5500i’s front panel), and allows the user to archive and re- store presets, automation lists, and system setups (containing I/O levels, digital word lengths, GPI functional assignments, etc.).
SNMP support The SNMP (Simple Network Management Protocol) features allow you to monitor your Optimod’s status and to send Alarm notifications via your Optimod’s Ethernet connection to your network.
OPTIMOD-FM 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 5500i’s GPI port or the 5500i PC Remote application), or by automation to permit broadcast system test and alignment or “proof of performance” tests.
OPTIMOD-FM contains a built-in line-up tone generator, facilitating quick and accurate level setting in any system.
OPTIMOD-FM's software can be upgraded by running Orban-supplied downloadable upgrade software on a PC. The upgrade can occur remotely through the 5500i’s Ethernet port or serial port (connected to an external modem), or locally (by connecting a Windows® computer to the 5500i’s serial port through the supplied null modem cable).
Stand-Alone Stereo Encoder Operation
Starting with v1.1 software, improved DSP code allows changing between normal two-band and five-band audio processor modes and stand-alone stereo encoder modes via a smooth cross-fade. This facilitates switching between pre- processed network feeds (where only overshoot limiting is needed) and local origination (where full audio processing is required).
The sample rate is 64 kHz and multiples thereof, up to 512 kHz. The internal audio bandwidth is high enough to prevent overshoot caused by spectral truncation of the left/right input signals that are band-limited to 18 kHz or lower.
15, 16, or 17 kHz linear-phase lowpass filtering can be applied to the input signal. To minimize input/output delay, this filter can be bypassed, which is appropriate if the input signal is correctly band-limited by the audio processor driving the 5500i.
A left/right domain overshoot limiter is available. This combines look-ahead and band-limited clipping techniques to control STL-induced overshoots while minimizing artifacts. A dual-mode composite limiter is available. It can operate in either “Half-Cosine Interpolation” mode or conventional hard clipper mode. The “Half-Cosine” mode provides better separation and preservation of stereo imaging, while the “Hard” mode provides brighter sound because it creates waveforms that are closer to square waves. Both modes provide excellent spectral protection of the pilot tone and subcarrier regions. To ensure accurate peak control, the limiter operates at 512 kHz sample rate.
A high-accuracy ITU412 multiplex power controller is available, with user control over the multiplex power threshold. This allows you to compensate for overshoots in the signal path upstream from the 5500i, preventing excessive reduction of the multiplex power.
The input signal can be flat or pre-emphasized to 50 μs or 75 μs.
The 5500i can apply J.17 de-emphasis to the input signal.
Versatile remote control is available via RS232 serial, GPI, and Ethernet.
All normal 5500i inputs and outputs are available, including analog and digital inputs, two composite outputs with independent level controls, and two subcarrier inputs (one of which can be repurposed to emit a 19 kHz pilot reference output for RDS/RBDS generators).