Orban Optimod-FM 8600Si Audio Processor

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optimod_fm8600S

Orban Optimod FM 8600Si

Summary

The 8600Si offers Orban’s flagship 8600 “MX” audio processing technology in a compact, 1 rack-unit package. The 8600Si is available in two models – 8600Si-FM (processing for analog FM transmitters) and 8600Si-HD (processing for both analog FM and digital distribution channels). Via an upgrade kit, an 8600Si-FM can be upgraded to an 8600Si-HD at any time without removing the unit from the rack.

Features

The 8600Si uses a 2×40-line LCD display for basic setup functions, while serious sound designers will create custom presets via the 8600Si’s included PC Remote software and Ethernet connection. Compared to the Orban Optimod-FM 8500, the 8600Si’s MX processing provides 2-3 dB more high frequency energy, greater transient impact, and lower distortion.

Other important features include:

  • New “ratings-encoder loopthrough” allows a ratings encoder to be driven from one of the 8600Si’s AES3 digital outputs, while its Sync Input can be repurposed to receive the ratings encoder output prior to the 8600Si’s built-in stereo encoder. Running the processed signal through the ratings encoder minimizes the number of “low audio level” alarms.
  • 8600Si can accept a 10 MHz GPS or rubidium reference input to lock the 19 kHz pilot tone frequency to the reference. This minimizes areas of mutual interference in single-frequency networks.
  • Cool-running switching power supply saves energy.

Technical Specification

Technical Specification

Performance

Except as noted in the text, specifications apply for measurements from analog left/right input to stereo composite output and to FM analog left/right output.

Frequency Response (Bypass Mode): Follows standard 50µs or 75µs pre-emphasis curve ±0.10 dB, 2.0 Hz–15 kHz. Analog left/right output and digital output can be user-configured for flat or pre-emphasized output.

Noise: Output noise floor will depend upon how much gain the processor is set for (Limit Drive, AGC Drive, Two-Band Drive, and/or Multi-Band Drive), gating level, equalization, noise reduction, etc. The dynamic range of the A/D Converter, which has a specified overload-to–noise ratio of 110 dB, primarily governs it. The dynamic range of the digital signal processing is 144 dB.

Total System Distortion (de-emphasized, 100% modulation): <0.01% THD, 20 Hz–1 kHz, rising to <0.05% at 15 kHz. <0.02% SMPTE IM Distortion.

Total System L/R Channel Separation: >50 dB, 20 Hz – 15 kHz; 60 dB typical.

Polarity (Two-Band and Bypass Modes): Absolute polarity maintained. Positive-going signal on input will result in positive-going signal on output when HD Polarity and FM polarity controls are set to Positive.

Processing Sample Rate:  The 8600Si is a “multirate” system, using internal rates from 64 kHz to 512 kHz as appropriate for the processing being performed. Audio clippers operate at 256 kHz (and are anti-aliased), while the composite limiter operates at 512 kHz.

Peak Control at HD Output: The peak limiter is oversampled at 256 kHz, yielding a worst-case overshoot of 0.4 dB at the analog output and for all output sample rates. (To achieve this performance at 32 kHz output sample rate, it is necessary to set the 8600Si’s HD lowpass filter cutoff frequency to 15 kHz.)

Processing Resolution: Internal processing has 24 bit (fixed point) or higher resolution.

Installation
Delay

Defeatable Analog FM Processing delay:  0.27 to 16.384 seconds, adjustable in one-sample increments at 64 kHz sample rate to allow the delays of the analog and digital paths in the HD Radio system to be matched at the receiver output.

Minimum Processing Delay: Processing structure dependent. Typically 17 ms for normal latency Five-band, 13 ms for low-latency Five-band, 3.7 ms for ultra-low-latency Five-band, and 17 or 22 ms for 2-band, depending on crossover structure chosen. MX presets have approximately 270 ms delay.

Analog Audio Input

Configuration: Stereo.

Impedance: >10kΩ load impedance, electronically balanced.

Nominal Input Level:
Software adjustable from –9.0 to +13.0 dBu (VU).

Maximum Input Level:
+27 dBu.

Connectors:
Two XLR-type, female, EMI-suppressed. Pin 1 chassis ground, Pins 2 (+) and 3 electronically balanced, floating and symmetrical.
A/D Conversion: 24 bit 128x oversampled delta sigma converter with linear-phase anti-aliasing filter.

Filtering: RFI filtered, with high-pass filter at 0.15 Hz.

Analog Audio Output

Configuration: Stereo. Flat or pre-emphasized (at 50µs or 75µs), software-selectable.
Source Impedance: 50Ω, electronically balanced and floating.
Load Impedance: 600Ω or greater, balanced or unbalanced. Termination not required or recommended.

Output Level (100% peak modulation):
Adjustable from –6 dBu to +24 dBu peak, into 600Ω or greater load, software-adjustable.

Signal-to-Noise:
>= 90 dB unweighted (Bypass mode, de-emphasized, 20 Hz–15 kHz bandwidth, referenced to 100% modulation).

L/R Crosstalk:
<= –70 dB, 20 Hz–15 kHz.

Distortion:
<= 0.01% THD (Bypass mode, de-emphasized) 20 Hz–15 kHz bandwidth.

Connectors:
Two XLR-type, male, EMI-suppressed. Pin 1 chassis ground, Pins 2 (+) and 3 electronically balanced, floating and symmetrical.
D/A Conversion: 24 bit 128x oversampled, with high-pass filter at 0.15 Hz (–3 dB).

Filtering:
RFI filtered.

Digital Audio Input

Configuration: Stereo per AES3 standard, 24 bit resolution, software selection of stereo, mono from left, mono from right or mono from sum.
Sampling Rate: 32, 44.1, 48, 88.2, or 96 kHz, automatically selected.

Connector: XLR-type, female, EMI-suppressed. Pin 1 chassis ground, pins 2 and 3 transformer balanced and floating, 110Ω impedance.

Input Reference Level: Variable within the range of –30 dBFS to –10 dBFS.
J.17 De-emphasis: Software-selectable.

Filtering: RFI filtered.
Digital Audio Outputs

Configuration: Two outputs, each stereo per the AES3 standard. The outputs can be independently set to emit the analog FM processed signal, the digital radio processed signal, or the low-delay monitor signal. The FM processed signal can be configured in software as flat or pre-emphasized to the chosen processing pre-emphasis (50µs or 75µs). The digital radio processing chain receives the output of the multiband limiter and processes it through a look-ahead peak limiter that operates in parallel with the main FM peak limiting system. The DR and FM signals are always simultaneously available. Each output can apply J.17 pre-emphasis if desired.

Sample Rate: Internal free running at 32 kHz, 44.1 kHz, 48 kHz, 88.2 kHz, or 96 kHz, selected in software. (Use 44.1 kHz or higher for best peak control.) Can also be synced to the AES3 SYNC input or the AES3 digital input at 32 kHz, 44.1 kHz, 48 kHz, 88.2 kHz, and 96 kHz, as configured in software.

Word Length: Software selected for 24, 20, 18, 16 or 14-bit resolution. First-order highpass noise-shaped dither can be optionally added, dither level automatically adjusted appropriately for the word length.

Connector: XLR-type, male, EMI-suppressed. Pin 1 chassis ground, pins 2 and 3 transformer balanced and floating, 110Ω impedance.

Output Level (100% peak modulation):
–20.0 to 0.0 dBFS software controlled.

Filtering: RFI filtered.

Frequency Response (Digital Audio Output (from Digital Radio Processing Chain)): For output sample rates of 44.1 kHz and above, the frequency response from input to DR-configured output is ±0.10 dB, 2.0 Hz – 20 kHz; flat or with J.17 pre-emphasis applied. The user may specify lowpass filtering to constrain the bandwidth to 15, 16, 17, 18, or 19 kHz.

Relative Time Delay between FM and HD Outputs:
Depends on setting of analog processing channel diversity delay. Once set, this delay is constant regardless of processing preset in use.
Wordclock/10 MHz Sync Reference

Configuration: Accepts 1x wordclock or 10 MHz reference signals, automatically selected. The DSP master clock can be phase-locked to these signals, which in turn phase-locks the 19 kHz pilot tone frequency, facilitating singe-frequency network operation. The digital output sample frequency can also be locked to these signals.

Level: Unit will lock to 1x wordclock and 10 MHz squarewaves and sinewaves having a peak value of 0.5 V to 5.0 V.

Connector:
BNC female, grounded to chassis, non-terminating to allow reference signals to be looped through via an external BNC “tee” connector (not supplied).
AES3id Input

Configuration:
The Wordclock/10 MHz Sync Reference can also be configured as an AES3id digital audio input to drive the input of the stereo encoder. This facilitates a “ratings encoder loop-through” connection, where the input of the ratings encoder is driven from one of the 8600Si’s AES3 outputs and the encoder’s output is returned to the AESid input. When not being used in ratings encoder loop-through mode, this input can receive an AES3id or AES11id sample rate reference signal to which the 8600Si’s digital outputs can be locked.

Connector: BNC female, grounded to chassis, terminated with 75Ω. For short cable runs, there is usually no problem in driving this with an AES3 (110Ω) signal. If the cable is long enough to cause digital audio reception errors due to impedance mismatch, a 110Ω/75Ω transformer should be placed in-line.

Composite Baseband Outputs

Configuration: Two outputs, each with an independent software-controlled output level control, output amplifier and connector.
Source Impedance: 0Ω voltage source or 75Ω, jumper-selectable.

Load Impedance: 37Ω or greater. Termination not required or recommended.

Maximum Output Level: +16.0 dBu (13.82Vp-p).
Pilot Level: Adjustable from 6.0% to 12.0%, software controlled.
Pilot Stability: 19 kHz, ±1.0 Hz (10 degrees to 40 degrees C).|

D/A Conversion: 24-bit
Signal-to-Noise Ratio: >= 85 dB (Bypass mode, de-emphasized, 20 Hz – 15 kHz bandwidth, referenced to 100% modulation, unweighted).

Distortion: <= 0.02% THD (Bypass mode, de-emphasized, 20 Hz – 15 kHz bandwidth, referenced to 100% modulation, unweighted).

Stereo Separation: >50 dB, 20 Hz – 15 kHz; 60 dB typical.

Crosstalk-Linear: <= –80 dB, main channel to sub-channel or sub-channel to main channel (referenced to 100% modulation).

Crosstalk-Non-Linear: <= –80 dB, main channel to sub-channel or sub-channel to main channel (referenced to 100% modulation).

38 kHz Suppression: >= 70 dB (referenced to 100% modulation).
76 kHz & Sideband Suppression: >= 80 dB (referenced to 100% modulation).

Pilot Protection: 60 dB relative to 9% pilot injection, ±250 Hz (up to 2 dB composite processing drive).

Subcarrier Protection (60-100 kHz): >= 70 dB (referenced to 100% modulation; with up to 2 dB composite limiting drive; measured with 800 line FFT analyzer using “maximum peak hold” display).

57 kHz (RDS/RBDS) Protection: 50 dB relative to 4% subcarrier injection, ±2.0 kHz (up to 2 dB composite processing drive).

Connectors: Two BNC, shell connected to chassis ground, EMI suppressed.

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