Orban
Optimod-AM 9100 B2

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Overview

Audio Processor

The 9100B2 is a complete audio processing system for AM stereo. It provides automatic gain control to ride levels, high-frequency boost to compensate for the roll-off in receivers (for a brighter sound), and a six-band limiter with distortion-canceling clipper for a very loud and clean sound. OPTIMOD-AM dramatically improves AM station fidelity and perceived loudness, easily overpowering competitors using other processors.

Features

Specifications

Performance
Frequency Response

No Optional Filter (PROOF mode): Better than ±1.0dB, 50-12,000Hz.
NRSC Filter Installed (PROOF mode): Better than ±1.0dB, 50-9,500Hz.
ITU-R Filter Installed (PROOF mode): Better than ±1.0dB, 50-4,500Hz. (or 5,000Hz, 5,500Hz, or 6,000Hz, as ordered).
Noise: >65dB (referenced to 100% modulation), 30-20,000Hz.

Total System Distortion

PROOF mode, 100% modulation: <0.2% THD, 50-9,500Hz (or to cutoff frequency of CCIR filter).

Stereo Separation

PROOF Mode: >25dB, 50-5,000Hz; 30dB typical.
Dynamic: >30dB typical.

Installation
Audio Input

Configuration: Left and right.
Impedance: >10k ohm load impedance, electronically-balanced with true instrumentation amplifier.
Sensitivity: -30dBu to +10dBu to produce 10dB AGC gain reduction.(0dBu=0.775Vrms).
Connector: Barrier Strip (#6 screw), EMI suppressed.

Audio Output

Configuration: Outputs for two transmitters, each with independent TX EQ and 18-turn screwdriver-adjust OUTPUT ATTENUATOR control. Stereo outputs are left-and-right or sum and difference, selectable with internal jumpers.
Impedance: 290 ohm source impedance, independent of OUTPUT ATTEN setting, electronically-balanced to ground. Recommended load impedance 600 ohm ±20%.
Peak Output Level: Adjustable from 0 to >+20dBu with 18-turn OUTPUT ATTEN controls (0dBu=0.775Vrms).
Connector: Barrier Strip (#6 screw), EMI suppressed.

Remote Control

Function: Switches one of four sets of transmitter equalizer controls: DAY/TX1, DAY/TX2, NIGHT/TX1, NIGHT/TX2.
Voltage: 6 to 24V AC or DC, momentary or continuous, optically-isolated. A voltage source is supplied on the rear panel.
Connector: Barrier strip (#6 screw), EMI suppressed.

Power

Requirements: 115/230VAC (switch-selectable), ±15%, 50-60Hz, 38VA.
Connector: IEC; detachable 3-wire power cord supplied. AC is EMI suppressed.
Ground: Circuit ground is independent of chassis ground; both appear on terminal strip on rear panel for strapping as required.

Environmental

Operating Temperature Range: 0-50 degrees C. (32-122 degrees F.)
Humidity: 0-95% RH, non-condensing.

Dimensions

19 inches (48.3cm) wide, 7 inches (17.8cm) high, 12.5 inches (31.2cm) deep. Requires 4 rack units.

Weight

9100B2 (stereo): 27lb (12kg) net; 41lb (19kg) shipping.

Access

Circuitry (except for power supply regulator) is on plug-in cards. All circuitry and user setup adjustments available from front panel without removing unit from rack. Control access door is fitted with a lock to prevent unauthorized adjustments.

Circuit Characteristics
Input Conditioning

High-Pass Filter: Third-Order elliptical with 50Hz cutoff and 0.5dB passband ripple; deep 25Hz notch to protect C-QUAM pilot tone and to reject automation cuetones; -0.5dB @ 50Hz, -45dB @ 25Hz, -27dB @ 20Hz. Low-Pass
Filter: Rolls off frequencies above ordered cutoff at a rate exceeding 24dB/octave.
Phase Scrambler: All-pass network makes peaks more symmetrical to best utilize the capabilities of the processing.

Broadband AGC

Attack Time: SINGLE, approximately 200ms; MULTI, program-controlled, varies according to program dynamics and amount of gain reduction.
Release Time: SINGLE, approximately 3dB/second; MULTI, program-controlled, varies according to program dynamics and amount of gain reduction.
Compression Ratio: Greater than 10:1.
Threshold of Compression: Controlled by input attenuators. Stereo Operation: Gains of left and right channels track to avoid stereo perspective shift.
Total Harmonic Distortion (at VCA output, OPERATE mode): Less than 0.05% 50-9,500Hz, +10 to -15dB gain reduction.
Available Gain Reduction: 25dB.
Gating: Gain will freeze, then drift slowly to 10dB gain reduction, if input level drops below the threshold set by front panel GATING control.

Bass Receiver Equalizer

Type: Quasi-parametric second-order peak boost.
Control: Bandwidth variable from 4 to 0.5 octaves (Q=0.3 to 1.4), TUNING variable 70 to 110Hz, EQ boost variable 0 to +6db.

High Frequency Receiver Equalizer

Curve Shape: Determined by plug-in "Personality Module." Four supplied.
Curve Characteristics: BLUE module: NRSC-standard modified 75microseconds pre-emphasis, +2.5dB @ 2kHz, +6.9dB @ 5kHz, +10dB @ 10kHz. RED, YELLOW, and GREEN: Three families of third-order shelving curves whose ultimate HF boost is adjustable with the HF EQ controls.

Crossover Filters (US Patent No. 4,412,100)

Filters: 150Hz low-pass, 420Hz band-pass, 700Hz band-pass, 1.6kHz band-pass, 3.7kHz band-pass, 6.2kHz high-pass.
Selectivity: 18dB/octave.
Topology: Parallel "distributed crossover."
Combined Frequency Response-Static: ±0.5dB, 50-9,500Hz.
Combined Frequency Response-Dynamic: Phase interaction between filters will not cause audible dips in frequency response.

Six-Band Limiter

Attack Time: Program-controlled, adjusted according to band frequency.
Release Time: Program-controlled, adjusted according to band frequency. Employs delayed release for distortion reduction.
Gain Reduction: Bands 1-5, 0-25dB; Band 6, 0-30dB.
Distortion Cancellation: All clipper-induced distortion in upper four bands canceled better than 30dB below 1.8kHz. Additional distortion reduction provided as a function of frequency in each band.
Variable-Gain Element: Proprietary Class-A VCA.

Stereo Control Circuitry


C-QUAM Stereo-75% Modulation Limiter: Jumperable in/out. Asymmetrical clipping in L and R channels. Clipping overdrive under conditions of high separation is prevented by dynamic gain reduction in L-R channel prior to L and R clipping (dynamic blend). L-R gain reduction is constrained to 6dB or less as required by program material. Mono receivers are unaffected, retaining full loudness.
Stereo Enhancer: Control on card. Permits increasing gain of L-R channel up to 6dB.
Stereo L-R High-Pass Filter: Jumperable in/out. 200Hz, 30dB/octave filter in L-R channel, phase-matching all-pass filter in L+R channel.

Output Low-Pass Filter

Type: NRSC units are provided with three switchable filters, 12kHz, 10kHz NRSC-standard, and 5.0kHz. ITU-R units are provided with two switchable filters, CCIR/EBU (4.5kHz, 5.0kHz, 5.5kHz, or 6.0kHz, as ordered), and 12kHz. All filters phase-corrected and overshoot-free when observed at processor output.
Characteristic-NRSC: Non-Linear over shoot-compensated, ±0.75dB to 9.6kHz. Guaranteed to meet the NRSC-1 power spectrum specification without the need for further low-pass filtering prior to the transmitter.
>Characteristic-IT-R: Non-linear overshoot-compensated, ±0.75dB to specified filter cutoff frequency. Guaranteed to meet the CCIR power spectrum specification (Recommendation 328-5) without the need for further low-pass filtering prior to the transmitter.
Characteristic-12kHz: Fifth-order elliptical filter, -0.5dB @ 12kHz.
Characteristic-5.0kHz: Auxiliary Filter Supplied with NRSC Units: 30dB/octave, -0.5dB @ 5kHz.
Switching: Jumper-selectable to follow DAY/NIGHT switching in any combination.

Transmitter Equalizer

Low Frequency Tilt Equalizer: Proprietary phase/magnitude compensation introduces adjustable positive slope tilt to the output waveform to cancel negative-slope tilt typical of older-technology transmitters. Independent control of very low frequency compensation available to avoid saturation and non-linear low frequency power handling capacity.
High Frequency Shelving Equalizer: Adjustable breakpoint shelving equalizer creates controlled undershoots in high frequency transient waveforms to prevent RF envelope overshoot due to excessive Q in transmitters, phasors, and/or antenna systems, or due to poor transient response in audio or modulator stages.
High Frequency Delay Equalizer: Introduces added time delay selectively into the spectrum to compensate for non-constant group delay in the transmitter/antenna system, thus optimizing transient response by creating approximately constant time delay at all frequencies within the audio bandwidth.
Controls: Four independent sets provided, DAY/TX1, DAY/TX2, NIGHT/TX1, NIGHT/TX2.
Switching: From the front panel or remotely.
Indication: Front panel LEDs.

Proof Test Mode

AGC and Six-Band Limiter: Defeats gain reduction. Circuitry is not bypassed.

Warranty

One year, parts and labor. Subject to limitations stated in our Standard Warranty.

Specifications subject to change without notice.

Notes

Increased Coverage and Improved Sound Quality

Staying Competitive with FM OPTIMOD-AM enables AM transmission systems to significantly increase coverage and achieve dramatic improvements in sound quality-voice or music-without sacrificing loudness. When equipped with OPTIMOD-AM, music-oriented stations can recapture audience from FM outlets by providing comparable fidelity to those listeners using less-expensive auto, portable and compact home systems. With OPTIMOD-AM processing, news/talk formats project voice with more impact, and hold listeners longer in marginal signal strength areas.

Loud, Clear and Consistent OPTIMOD-AM's clean, effortless sound is the result of several subsystems working synergistically to solve the problems inherent in AM transmission. First, an AGC delicately balances levels over a 25dB input range to assure consistent processing. An adjustable high frequency boost pre-compensates for the rolloff in most AM recievers. The Six-Band limiter produces the loudness, consistent in texture and tonal balance. Voice stands out; telephone calls, actualities and other unpredictable sources are pulled "out of the mud." Next, OPTIMOD-AM's patented technology controls peaks at the outputs of the six bands without affecting average level or introducing distortion. Finally, a set of amplitude and group delay equalizers compensates for tilt and overshoot in the transmitter/antenna system that can compromise signal loudness. The combined result is a sound with consistent loudness and crisp presence, while totally free of the pumping, grittiness and "squash" that too often accompany a loud signal.

A Complete System for Mono or Stereo OPTIMOD-AM is available for stereo (9100B2). Mono units may be upgraded to stereo in the field. An 8200ST OPTIMOD-Studio Chassis is recommended to optimize STL performance when the OPTIMOD-AM unit is located at the transmitter site.