Technology

Multichannel POWER Amplifiers

The recent release of the first DVD-A titles from Warner Music Group has spurred renewed interest in multichannel amplifiers for surround sound applications. 3/01/2001 7:00 AM Eastern

The recent release of the first DVD-A titles from Warner MusicGroup has spurred renewed interest in multichannel amplifiers forsurround sound applications. For those recording and mixingfacilities expanding into surround sound work, multichannel ampsoffer a cost-effective solution for driving 5.1 loudspeakersystems. Even for stereo monitor setups, multichannel amplifiersmay be appropriate for powering two- and three-way referencemonitors. But multichannel amps have other applications, and, foryears, they have been found in sound systems for movie theaters andlive shows and are commonly used in a wide range of fixedinstallations, such as music venues, theme parks and sportsfacilities.

Because multichannel amps are used in a range of applications,feature sets and specifications vary. For example, cinema and soundreinforcement applications generally require direct low-impedanceamplifier outputs capable of driving 2-, 4- or 8-ohm loads. Ampsdesigned for live sound applications must often drive multiplespeaker cabinets, so hefty power output is a requirement. Becausesound reinforcement systems also need to be set up and broken downquickly, amps used in this application generally feature bindingposts and/or Speakon outputs, whereas amps intended for permanentinstallations more often offer barrier strips. Weight is also afactor: In order to reduce shipping weight and minimize riggingloads when amps are flown along with speaker clusters, ampsdesigned for touring applications must also be as small and lightas possible.

A recent trend in amplifier design is the inclusion of acomputer interface, which allows for remote monitoring of theclipping and thermal status of amplifiers. Some computer monitoringsystems allow for comprehensive remote control of all amplifierparameters, a useful feature when aligning or troubleshootinglarge, fixed installations and complex live sound rigs. Someamplifier models allow for optional add-on DSP modules, whichprovide onboard processing functions, such as delay, EQ, filteringand crossover facilities. Such local DSP, integrated with amultichannel power amp, offers obvious benefits. Rather thansending processed signals via multiple long feeds from youroriginating signal source out to your amps, you can send a stereofeed to your remotely placed DSP and split the processed signalfrom there out to your various feeds. Say goodbye to all that extraexpensive cabling and clutter!

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

As you might expect, not all products fit neatly into theseexclusive classifications. Some amps can serve multipleapplications, either straight out of the box or after optionalmodifications. But whatever the intended application, multichannelamplifiers offer significant space and cost savings over multiplemono-block or stereo amps. Because there is no need for discretepower supplies for each channel in a multichannel amp, everythingcan 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 threeor more channels and were first introduced in 1999 or later areincluded here. To learn more about a particular model, check outthe accompanying sidebar for the manufacturer's contactinformation. Feel the power!

AB INTERNATIONAL MODELS 6600A, 6600JS

Amplified Design International is the manufacturer for ABInternational Products. The AB International Professional SeriesModel 6600A ($3,500) is a full-featured, 4U, rackmountable,6-channel amplifier capable of delivering 400 watts into eightohms, 600 watts into four ohms or 750 watts into two ohms. Featuresinclude three individual power supplies; six independent, balancedand unbalanced inputs; outputs on five-way binding posts; detentedlevel controls; comprehensive protection circuitry; Signal Presentand “Soft Clip” indicators; dual, temperature-activatedfans; and Stereo/Bridge switches for each pair of channels. Channel6 features a fourth-order Linkwitz-Riley lowpass filter, set at 100Hz and selectable from the rear panel for use with a subwoofer.Input sensitivity is selectable internally. Optional 70Vtransformers are available for use with distributed systems.

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

ASHLY AUDIO POWERFLEX 6250

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

AUDIOCONTROL INDUSTRIAL MODELS 510, 710

Models 510 and 710 are 3U, 12-channel amplifiers intended formultizone installations. Each channel is discrete and provides 50watts of power at eight ohms, built-in limiting, and short circuitand DC offset protection. Channel pairs may be bridged. Eachchannel pair also has controls for input gain, programmablehighpass filters and defeatable signal sense mute. Other featuresinclude a remote power-on trigger, phoenix-type connectors for I/O,fan-free operation and an optional rackmount kit. Model 710 adds6-band custom equalization for small speakers to the featureset.

BRYSTON 6B ST

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

C AUDIO PULSE 4×300

The 4-channel Pulse 4×300 ($1,650 list) is part of CAudio's Pulse Series line of amplifiers. Like other amplifiers inthis line, the 4×300 uses state-of-the-art Switched mode powersupplies to dramatically reduce weight and provide consistentperformance at all power levels. The 2U, rackmountable 4×300delivers 170 watts into eight ohms, 300 watts into four ohms or 330watts into two ohms. Standard features include electronicallybalanced inputs on XLR connectors; indented level controls;extensive protection circuitry and associated status indicators;relay-less muting circuits for power-up and -down; and twovariable-speed cooling fans. Channels may be switched for bridgedoperation in pairs. Outputs may be ordered as binding posts orSpeakon connectors. Other options include internal analogcrossovers, input transformers, fan filters, front and rear racksupport brackets, and remote control and monitoring facilities overa 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 PowerAmplifier ($899.95 suggested retail). The 2U, rackmountableXPM-3000 features two satellite channels and one subwoofer channel.The amp delivers 200 watts to the satellites and 220 watts to thesub at eight ohms. A two-way, 60Hz Linkwitz-Riley crossover handlesthe transition between the satellite and subwoofer channels. Thesubwoofer channel offers a switchable low-frequency boost (flat, +3dB or +6 dB) at 40 Hz and can easily serve dual subwoofers via itstwo parallel, five-way binding posts (120V unit only). Otherfeatures include post crossover line-level outputs for chainingadditional speakers, comprehensive protection circuitry andtwo-speed dual fans. Inputs are on balanced XLR andbalanced/unbalanced 1¼4-inch jacks. Outputs are via five-waybinding posts for 120V models and Neutrik Speakon connectors for230V models.

QSC CX204V, CX254, CX404, DCA1644 and DCA1824

QSC Audio offers three multichannel amplifiers in the CX Seriesproduct line and another two in the DCA Series. Each of the fivemodels fits four amplifier channels into a lightweight, 14-inchdeep, rackmountable 2U chassis. The company's exclusivePowerWave switching power supplytechnology, 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 soundsystems, with the CX204V rigged to service 70-volt distributedsystems, and the CX254 and CX404 intended for cinema soundapplications. All three models in the CX Series have the same$1,400 list price and feature bridgeable channel pairs; selectablehighpass filters; detachable, Euro-style input connectors; barrierstrip output connectors; comprehensive protection circuitry andfront panel status indicators; a low-noise, variable-speed fan;gain controls detented in 1dB increments (for fast setup andaccuracy); an integrated security cover; and an Ethernet-based HD15DataPort. The DataPort interfaces with a PC running the company'soptional QSControl software ($2,800). QSControl provides remotecomputer monitoring and control of clipping and thermal status forall 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 supplies170 watts at eight ohms, 250 watts at four ohms or 450 watts at twoohms per channel. The CX404 is not rated for 2-ohm operation but isthe 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) are4-channel models geared toward cinema sound applications. TheDCA1824 was designed for driving surround channels, with eachamplifier channel capable of powering up to four 8-ohm speakers inparallel for a total of up to 16 speakers. The amp supplies 170watts at eight ohms, 250 watts at four ohms or 450 watts at twoohms. Its more powerful sibling, the DCA1644, delivers 250 wattsinto eight ohms or 400 watts into four ohms (the DCA1644 is notrated for 2-ohm operation) and is better suited for powering screenchannels in small to medium theaters. Pairs of channels can bebridged in both models for powering tri-amp speaker systems. Otherfeatures common to both models include inputs on 3-pin, detachableterminal blocks; outputs on a safety-shrouded barrier strip; twoHD15 DataPorts (one for each channel pair); a variable speed fan;comprehensive protection circuitry and status indicators; and again control security cover.

YAMAHA XM6150, XM4220

Yamaha's versatile XM6150 and XM4220 power amplifiers ($899each) can power standard speaker systems and/or 70V distributedsystems, in any combination. All channels can be used for the sametype of application, or you can mix and match channels fordifferent systems. Both the XM6150 and XM4220 incorporate Yamaha'sexclusive EEEngine technology for extremely high-power efficiency.Each of the XM6150's six channels delivers 100 watts into eightohms or 120 watts into four ohms. The XM4220's four channels eachsupply 140 watts into eight ohms or 180 watts into four ohms. Bothmodels feature bridge on/off switches for each channel pair,allowing you to simultaneously operate some channels in Bridgedmode and others in Unbridged. Other features common to both unitsare a parallel input switch that allows you to drive all amplifierchannels from one source/input; rear panel attenuators; highpassfilter switches; input connections on balanced XLRs and Euro-blockterminals; outputs on five-way binding posts; comprehensive circuitprotection and system indicators; a variable-speed fan; and alightweight, 8.2 lbs. chassis.


Michael Cooper is a Mix contributing editor and owner of MichaelCooper 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