Orban Optimod-FM 5501e

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Brand: OrbanOrban


Orban’s 5501e is an FM stereo audio processor that provides the functionality of Orban’s stand-alone Optimod-FM 5500 on a PCIe card for PCs running Windows 7 or higher. It implements two-band and five-band processing, a stereo encoder with Orban’s Half-Cosine Interpolation composite limiter, and a low-latency monitor output. In addition to this classic Optimod-FM audio processing, the 5501e provides a BS.412 multiplex power controller to comply with European regulations.

 Because the 5501e implements audio processing via onboard DSP chips, it uses few CPU resources. With a PCIe expansion chassis, one computer can run as many as eight 5501e cards.

Via a multi-pin connector on its rear flange, the 5501e offers a full complement of hardware inputs and outputs, both analogue and AES3 digital. In addition to the usual left/right analogue and AES3 digital inputs and outputs, the 5501e supplies two analogue composite outputs and two analogue SCA inputs. It has two sync inputs: AES11 sync, and wordclock / 10 MHz (automatically selected). These allow the 5501e’s output sample rate and pilot frequency to be locked to an external reference like GPS.

Additionally, the 5501e appears to Windows as a sound card that provides a Recording input and Playback output, so it can accept a left/right audio input and emit a processed L/R output through the normal Windows Sound mechanism. For example, a 5501e can directly accept the output of playout software that runs on the same computer. Moreover, integration with Windows Sound allows the 5501e to be interfaced to an audio-over-IP distribution system using an Ethernet port and audio-over-IP distribution driver on the host computer.

Like Orban’s popular 1101e audio processor / soundcard, the 5501e can be controlled via 5501e PC Remote software running on the same computer as the 5501e, or on a network. This software supports a connection list that can include multiple 5501e cards, so it can easily connect to a given card, whether local or in another computer on the network.

Absolute Control of Peak Modulation

    The 5501 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 5501 provides pre-emphasis limiting for the two standard pre-emphasis curves of 50ms and 75ms. Its pre-emphasis control is seldom audibly apparent, producing a clean, open sound with subjective brightness matching the original program.

    The 5501 achieves extremely tight peak control at all its outputs — analogue left/right, AES3 left/right, and composite baseband.

    By integrating the stereo encoder with the audio processing, the 5501 eliminates the overshoot problems that waste valuable modulation in traditional external encoders. The stereo encoder has two outputs with independent level controls.

    The 5501 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 5501’s audio outputs and stereo encoder.

    Anti-aliased clippers running at 256 kHz sample rate prevent any trace of “digital clipper” sound.

    A Bypass Test Mode permits broadcast system test and alignment or “proof of performance” tests.

    The 5501 contains a built-in line-up tone generator, facilitating quick and accurate level setting in any system.

Flexible Configuration

    The 5501 includes analogue and AES3 digital inputs and outputs. Both digital input and digital outputs are equipped with sample-rate converters and can operate at 32 kHz, 44.1 kHz, 48, 88.2, 96 and 192 kHz sample rates. The pre-emphasis status and output levels are separately adjustable for the analog and digital outputs.

    The 5501 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 analogue inputs are transformerless, balanced 10kW instrumentation-amplifier circuits, and the analogue outputs are transformerless balanced, and floating (with 50W impedance) to ensure highest transparency and accurate pulse response.

    The 5501 has two independent composite baseband outputs with digitally programmable output levels and robust line drivers. A given AES3 digital output can configured to emit the composite baseband signal at 192 kHz.

    The 5501 has two subcarrier inputs that are digitized and mixed into the composite output.

    The 5501 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 5501 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 5501-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 5501 has a Wordclock/10 MHz Sync Reference Input, 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 5501 in single-frequency network applications.

    The 5501 can delay its output by as much as 16 seconds. This delay can be used as the diversity delay in HD Radio™ installations, which allows the 5501’s stereo encoder (including composite limiter) to be used in an HD Radio installation.

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 5501 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 crossfade.

    The 5501 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 5501 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 5501’s Two-Band processing structure is phase-linear to maximize audible transparency.

    The 5501 can import and run any 8300, 8400, or 8500 “LL” (Low-Latency) preset via the 5501 PC Remote application. This means that you can use an 8300, 8400, or 8500 to develop presets for 5501 if you do not use features in the other processors not supported by the 5501. (If you try to import a preset that uses features unsupported by 5501, the 5501 will interpret that preset as best it can by using the available 5501 features.


    5501 PC Remote software is a graphical application that runs under Windows 7/8/10. The software can act as a client to control any number of 5501e cards, either locally or in other PCs on your network via TCP/IP addressing. Other Orban software offers a server function, allowing other computers on your network to address cards located in your PC. (This server software is installed automatically as part of the 5501e installation process and runs as a Windows Service.)

    PC Remote’s I/O Mixer window permits versatile routing and switching of processed and unprocessed audio from and the 5501e’s inputs and outputs, and to and from the host computer's WAVE audio.

    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.

    Terminal Control API for network or localhost control and automation of all I/O Mixer functions and Preset switching. Status is broadcast to all active clients.

    Serial Control API allows the 5501e to be controlled either by ASCII serial commands or by a serial-to-contact-closure device.