Technology Showcase: Remote-controlled and Networked Power Amplifiers
Jul 6, 2009 12:00 PM, By Bennett Liles
New options for controlling your network from any location.
With the coming of digital audio networks and new protocols augmenting existing serial control technologies, the world of power amplifier control and monitoring has become an increasingly exciting and innovative realm. New options abound for multiple-channel control and increasingly nuanced parameter manipulation by PC from any location. Coupled with new efficiency in power versus size and weight, power amplifiers represent a new crossroads of technologies that are still developing and bringing new ideas to life in the real world. Many are capable of using slide-in hardware to custom-design the units to interface with all the leading digital audio networks, and most also provide older and robust serial control and monitoring methods. Let’s have a look at what the field currently offers.
The 2-channel NE series amplifiers from Ashly Audio are designed for the installation market, and they offer 8V/4V stereo, 8V mono, and constant 100V output to match any installation scenario. The ne2400 provides 1200W per channel at 4V. The amps in this series are all equipped with XLR input connections and Speakon/Euroblock output connectors. Their balanced analog inputs can be used in bridged mono mode, and all models come equipped with an 80Hz high-pass filter, input-sensitivity switch, and Ethernet connections for use with Ashly’s Proteane software. Using this, units that have the factory-installed DSP module can be configured with DSP blocks for dynamics control, gain functions, graphic and/or parametric EQ, high- and low-pass filters, time delay, metering, and test signal generation. Assignable routing in the mixer section allows any input to drive any combination of outputs. Global parameters of a unit’s control surface and DSP section can be stored and retrieved from a file. Up to 35 individual DSP function parameters within and across both channels of the amplifier can be stored and recalled as a set using the Proteane software application on a control PC over the Ethernet connection.
The BGW Systems VX series amplifiers use the 15-pin faastLink D-sub interface for remote control and signal processing, enabling users to monitor crucial aspects of amplifier performance. The VX880 can put 900W into each channel at 8V, 1500W per channel at 4V, or 2300W in bridged mode, and it handles 1400W at 70V. The modes are set by switches on the rear panel. The unit produces less than 0.008 percent intermodulation distortion at 8V output. It demonstrates a rise time of 6µs and a slew rate of 20V/µs in stereo mode and 40V/µs in mono mode. The voltage gain is 34.7dB, and input sensitivity is 0.775Vrms for rated 8V output. Each channel includes a detented 21-position rotary control input attenuator in 1dB attenuation steps. The cooling is accomplished by a continuously variable fan speed, providing front-to-back air flow based on accurate temperature sensing on the heatsink modules. FaastLink was co-invented by a group of manufacturers including BGW Systems. The feature is standard on VX series amplifiers and optional on the C and GT series. The 15-pin connector accepts audio input, sends power to an external device, and sends signals monitoring amplifier output voltages and currents as well as other important parameters.
Power amps in the Vortex series from Camco use switched-mode power supplies (SMPS) to enable the units to pack more power into a smaller, lighter package. The Vortex 200V provides 3.2kW per channel at 4V, 6.4kW in monobridge mode at 8V, and 6.4kW in parallel mono at 2V. The rear panel includes the Camco Audio Interface (CAI), a bus system that connects with a two-core insulated cable through which all major functions can be monitored and controlled remotely using a master PC. With CAI, the user can mute and control the output level of each channel independently; switch the Vortex in and out of standby mode; and monitor temperature, output signal, clip, and output current. For moderate distances, a telephone cable with RJ-12 connectors can be used, and for longer control distances, RS-485 can be used. Using the second CAI connection, the control signals can be looped onto additional Vortex amps or other CAI-controlled devices. A linear network topology is recommended with 100V termination at its end. The CAI address selection procedure is performed on the front panel using a recessed enter switch with visual indication on the associated front-panel LEDs.
The Ci series from Crest Audio is designed to fit the needs of system integrators in permanent installations requiring networking and remote control/monitoring features. Shipping in Q3 2009, the 8-channel Ci 20x8 offers the ability to operate at rated power of 200W per channel regardless of the load impedance from 4V to 70V. With the addition of the optional CMX 100V isolation transformer unit, 100V operation is available. Module bay accessories including the Nx CobraNet-8 enable the Ci series amps to use monitoring and control networks through Crest’s NexSys 4 software or Peavey MediaMatrix MWare or NWare applications. The NX CobraNet-8 supports all NexSys functions, DSP functions, and CobraNet digital audio I/O on a single Cat-5 cable. The module slides into a rear bay on the Ci series amplifiers to provide complete remote control and monitoring. It is also possible to use remote gain control through a control voltage input and to connect the fault output on each channel to other monitoring systems. The DSP control features include EQ, delay, and compression/limiting, while monitoring features allow Active Clip Limiting, Instantaneous Gain Modulation, I/O gain levels, thermal protection, fault, mute, and Ethernet data and link status. The Ci series amps will ship network-ready, and all have a four-character LED for control and monitoring of up to eight CobraNet audio channels.
Using its class-I amplifier technology and new software, Crown Audio has introduced the I-Tech HD series amplifiers primarily for installation applications. The DSP engine co-developed with BSS Audio and linear-phase FIR filters fine-tune the performance. Options include CobraNet and LevelMax peak and RMS power limiters and the new Firewall FIR filter technology are designed to improve mid-range clarity and off-axis response. There are 64 assignable filters with nine different filter types. DSP options include all-pass filters, up to 2 seconds delay per channel, and dual uncorrelated noise and sine wave generators. The rear panel includes digital AES/EBU connections and a standard 100Mbps CobraNet digital connection with RJ-45. Analog XLR connections include both input and link output. The front-panel LCD screen allows the user to control the amplifier’s attenuation and muting, configure parameters, and monitor error signals such as temperature and load supervision. The LCD also enables IP and HiQnet address setting and recall of DSP presets for quick reconfiguration to suit various amplifier applications. The front panel also offers speed-sensitive rotary level controls that advance in 0.5dB steps from 0dB to -100dB for channel 1 and 2 output levels. The same knobs are also used to select menu items and adjust parameter values displayed on the LCD control screen.
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