Multichannel POWER Amplifiers

Mar 1, 2001 12:00 PM, Michael Cooper

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The recent release of the first DVD-A titles from Warner Music Group has spurred renewed interest in multichannel amplifiers for surround sound applications. For those recording and mixing facilities expanding into surround sound work, multichannel amps offer a cost-effective solution for driving 5.1 loudspeaker systems. Even for stereo monitor setups, multichannel amplifiers may be appropriate for powering two- and three-way reference monitors. But multichannel amps have other applications, and, for years, they have been found in sound systems for movie theaters and live shows and are commonly used in a wide range of fixed installations, such as music venues, theme parks and sports facilities.

Because multichannel amps are used in a range of applications, feature sets and specifications vary. For example, cinema and sound reinforcement applications generally require direct low-impedance amplifier outputs capable of driving 2-, 4- or 8-ohm loads. Amps designed for live sound applications must often drive multiple speaker cabinets, so hefty power output is a requirement. Because sound reinforcement systems also need to be set up and broken down quickly, amps used in this application generally feature binding posts and/or Speakon outputs, whereas amps intended for permanent installations more often offer barrier strips. Weight is also a factor: In order to reduce shipping weight and minimize rigging loads when amps are flown along with speaker clusters, amps designed for touring applications must also be as small and light as possible.

A recent trend in amplifier design is the inclusion of a computer interface, which allows for remote monitoring of the clipping and thermal status of amplifiers. Some computer monitoring systems allow for comprehensive remote control of all amplifier parameters, a useful feature when aligning or troubleshooting large, fixed installations and complex live sound rigs. Some amplifier models allow for optional add-on DSP modules, which provide onboard processing functions, such as delay, EQ, filtering and crossover facilities. Such local DSP, integrated with a multichannel power amp, offers obvious benefits. Rather than sending processed signals via multiple long feeds from your originating signal source out to your amps, you can send a stereo feed to your remotely placed DSP and split the processed signal from there out to your various feeds. Say goodbye to all that extra expensive cabling and clutter!

Of course, multichannel amplifiers are also a critical component in fixed, multizone installations. These installations typically feature distributed systems where clusters of small speakers are permanently installed in ceilings for paging and/or background music delivery. Distributed systems typically use “70-volt” (70.7V to be exact; 100V in Europe) amplifiers to drive numerous, relatively low-powered speakers. So a critical consideration here is to provide as many channels as possible in as small a chassis as possible. Such amps generally use barrier strips in lieu of binding posts (as do those intended for use in theaters) for more secure connections over time.

As you might expect, not all products fit neatly into these exclusive classifications. Some amps can serve multiple applications, either straight out of the box or after optional modifications. But whatever the intended application, multichannel amplifiers offer significant space and cost savings over multiple mono-block or stereo amps. Because there is no need for discrete power supplies for each channel in a multichannel amp, everything can fit conveniently into one chassis.

What follows is a list of the newest, top-of-the-line, multichannel power amplifiers. Only those amps that feature three or more channels and were first introduced in 1999 or later are included here. To learn more about a particular model, check out the accompanying sidebar for the manufacturer's contact information. Feel the power!

AB INTERNATIONAL MODELS 6600A, 6600JS

Amplified Design International is the manufacturer for AB International Products. The AB International Professional Series Model 6600A ($3,500) is a full-featured, 4U, rackmountable, 6-channel amplifier capable of delivering 400 watts into eight ohms, 600 watts into four ohms or 750 watts into two ohms. Features include three individual power supplies; six independent, balanced and unbalanced inputs; outputs on five-way binding posts; detented level controls; comprehensive protection circuitry; Signal Present and “Soft Clip” indicators; dual, temperature-activated fans; and Stereo/Bridge switches for each pair of channels. Channel 6 features a fourth-order Linkwitz-Riley lowpass filter, set at 100 Hz and selectable from the rear panel for use with a subwoofer. Input sensitivity is selectable internally. Optional 70V transformers are available for use with distributed systems.

AB International also offers the Model 6600JS ($3,750), which is a sonically advanced version of the 6600A and was developed specifically for state-of-the-art theater installations.

ASHLY AUDIO POWERFLEX 6250

Ashly Audio's new 6-channel Powerflex 6250 ($TBA) boasts an efficiency of greater than 80% due to its high-speed MOSFET switching design. The 3U, rackmountable unit delivers 150-watts RMS at eight ohms (250-watts RMS at four ohms) through six independent channels, and it can also be used in 3-, 4- and 5-channel configurations. Features include XLR/¼-inch combi and Euro-block input connections with level controls, a switchable highpass filter for each input, five-way binding posts for outputs, multiple protection circuits, and a quiet, two-speed fan. The Powerflex 6250 may also be configured as three independent 70V amplifiers in Bridged mode for paging applications. Initial shipments are scheduled for April 2001.

AUDIOCONTROL INDUSTRIAL MODELS 510, 710

Models 510 and 710 are 3U, 12-channel amplifiers intended for multizone installations. Each channel is discrete and provides 50 watts of power at eight ohms, built-in limiting, and short circuit and DC offset protection. Channel pairs may be bridged. Each channel pair also has controls for input gain, programmable highpass filters and defeatable signal sense mute. Other features include a remote power-on trigger, phoenix-type connectors for I/O, fan-free operation and an optional rackmount kit. Model 710 adds 6-band custom equalization for small speakers to the feature set.

BRYSTON 6B ST

New for Bryston is the 3-channel Model 6B ST ($TBA), a high-powered and rigorously engineered amp intended for recording studio use. Each channel consists of an independent amplifier module with its own power transformer and ±80V power supply. The 6B ST delivers a minimum of 300 watts into eight ohms or 500 watts into four ohms per channel. Both XLR/TRS 1¼4-inch combo jacks and RCA connectors are provided for each channel to accommodate balanced and unbalanced input signals, respectively. Outputs are on three-way, gold-plated binding posts. Features include rear panel input attenuators, external power-up terminals, a clip-sensing circuit for both inputs and outputs, and thermal over-temperature protection.

C AUDIO PULSE 4×300

The 4-channel Pulse 4×300 ($1,650 list) is part of C Audio's Pulse Series line of amplifiers. Like other amplifiers in this line, the 4×300 uses state-of-the-art Switched mode power supplies to dramatically reduce weight and provide consistent performance at all power levels. The 2U, rackmountable 4×300 delivers 170 watts into eight ohms, 300 watts into four ohms or 330 watts into two ohms. Standard features include electronically balanced inputs on XLR connectors; indented level controls; extensive protection circuitry and associated status indicators; relay-less muting circuits for power-up and -down; and two variable-speed cooling fans. Channels may be switched for bridged operation in pairs. Outputs may be ordered as binding posts or Speakon connectors. Other options include internal analog crossovers, input transformers, fan filters, front and rear rack support brackets, and remote control and monitoring facilities over a low-cost network that can address over 100 Pulse amplifiers.

GEMINI SOUND XPM-3000

New for 2001 is the XPM-3000 3-channel MOSFET Professional Power Amplifier ($899.95 suggested retail). The 2U, rackmountable XPM-3000 features two satellite channels and one subwoofer channel. The amp delivers 200 watts to the satellites and 220 watts to the sub at eight ohms. A two-way, 60Hz Linkwitz-Riley crossover handles the transition between the satellite and subwoofer channels. The subwoofer channel offers a switchable low-frequency boost (flat, +3 dB or +6 dB) at 40 Hz and can easily serve dual subwoofers via its two parallel, five-way binding posts (120V unit only). Other features include post crossover line-level outputs for chaining additional speakers, comprehensive protection circuitry and two-speed dual fans. Inputs are on balanced XLR and balanced/unbalanced 1¼4-inch jacks. Outputs are via five-way binding posts for 120V models and Neutrik Speakon connectors for 230V models.

QSC CX204V, CX254, CX404, DCA1644 and DCA1824

QSC Audio offers three multichannel amplifiers in the CX Series product line and another two in the DCA Series. Each of the five models fits four amplifier channels into a lightweight, 14-inch deep, rackmountable 2U chassis. The company's exclusive PowerWave switching power supply technology, which purportedly virtually eliminates hum and noise, is featured in all CX Series and DCA Series amps.

The CX Series is geared toward permanently installed sound systems, with the CX204V rigged to service 70-volt distributed systems, and the CX254 and CX404 intended for cinema sound applications. All three models in the CX Series have the same $1,400 list price and feature bridgeable channel pairs; selectable highpass filters; detachable, Euro-style input connectors; barrier strip output connectors; comprehensive protection circuitry and front panel status indicators; a low-noise, variable-speed fan; gain controls detented in 1dB increments (for fast setup and accuracy); an integrated security cover; and an Ethernet-based HD15 DataPort. The DataPort interfaces with a PC running the company's optional QSControl software ($2,800). QSControl provides remote computer monitoring and control of clipping and thermal status for all amps in the system. An optional, piggyback DSP module — the DSP-3 ($525) — is also available.

The CX204V supplies 200 watts per channel. The CX254 supplies 170 watts at eight ohms, 250 watts at four ohms or 450 watts at two ohms per channel. The CX404 is not rated for 2-ohm operation but is the most powerful amp in the CX Series line for driving 8-ohm loads (250 watts/channel) and 4-ohm loads (400 watts/channel).

QSC's DCA1644 and DCA1824 amplifiers (each $1,438 list) are 4-channel models geared toward cinema sound applications. The DCA1824 was designed for driving surround channels, with each amplifier channel capable of powering up to four 8-ohm speakers in parallel for a total of up to 16 speakers. The amp supplies 170 watts at eight ohms, 250 watts at four ohms or 450 watts at two ohms. Its more powerful sibling, the DCA1644, delivers 250 watts into eight ohms or 400 watts into four ohms (the DCA1644 is not rated for 2-ohm operation) and is better suited for powering screen channels in small to medium theaters. Pairs of channels can be bridged in both models for powering tri-amp speaker systems. Other features common to both models include inputs on 3-pin, detachable terminal blocks; outputs on a safety-shrouded barrier strip; two HD15 DataPorts (one for each channel pair); a variable speed fan; comprehensive protection circuitry and status indicators; and a gain control security cover.

YAMAHA XM6150, XM4220

Yamaha's versatile XM6150 and XM4220 power amplifiers ($899 each) can power standard speaker systems and/or 70V distributed systems, in any combination. All channels can be used for the same type of application, or you can mix and match channels for different systems. Both the XM6150 and XM4220 incorporate Yamaha's exclusive EEEngine technology for extremely high-power efficiency. Each of the XM6150's six channels delivers 100 watts into eight ohms or 120 watts into four ohms. The XM4220's four channels each supply 140 watts into eight ohms or 180 watts into four ohms. Both models feature bridge on/off switches for each channel pair, allowing you to simultaneously operate some channels in Bridged mode and others in Unbridged. Other features common to both units are a parallel input switch that allows you to drive all amplifier channels from one source/input; rear panel attenuators; highpass filter switches; input connections on balanced XLRs and Euro-block terminals; outputs on five-way binding posts; comprehensive circuit protection and system indicators; a variable-speed fan; and a lightweight, 8.2 lbs. chassis.


Michael Cooper is a Mix contributing editor and owner of Michael Cooper Recording in beautiful Sisters, Ore.

MANUFACTURER'S CONTACT INFORMATION

Amplified Design International
(AB International)
916/783-7800
www.abamps.com

Ashly Audio
800/828-6308
www.ashly.com

AudioControl Industrial
425/775-8461
www.audiocontrol.com

Bryston
802/334-1201
www.bryston.ca

C Audio
615/360-0277
www.c-audio.com

Gemini Sound
732/969-9000
www.geminidj.com

QSC Audio
800/854-4079
www.qscaudio.com

Yamaha
888/926-2424
www.yamaha.com






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