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This range of four-channel power amplifiers is intended for commercial and industrial public-address and sound-reinforcement applications where unquestionable long-term reliability is the primary consideration. The three models in the range, offer four channels of 120W, 240W and 400W output; pairs of channels may be operated in bridge mode. The steel 2U chassis has variable-speed, forced-air cooling while the protection circuitry includes clip-limiting and switch-on delay, together with DC, thermal, short-circuit and reactive load protection. The inputs are line-level and electronically balanced, VCA circuitry is provided for remote level control and an optional web monitor card permits monitoring of the amplifier's performance, via a standard Ethernet connection, and if connected to the internet, world-wide, even on a mobile phone.

The amplifiers are designed to deliver their full rated power into loads down to 4 ohms for long periods of time, while bridge mode uses a pair of channels to provide double the normal power into a load of 8 ohms. As well as theatres, leisure centres and other major venues, they are also aimed at applications in airport terminals, railways stations and similar large public spaces.

The substantial front panel, constructed from a cast aluminium facia sandwiched with a steel backing-plate, is dominated by two air-intakes for the variable-speed DC cooling fans. In the centre an inset panel houses LED indicators showing power status, signal presence, signal peak and protection system active for each of the four channels. A large rocker switch turns the amplifier on and off. Two protruding lugs provide protection should the amplifier be placed on the front panel, perhaps during installation.

The rear panel also has two grilles, for air to flow out past the internal heat-sinks. Power is connected by an IEC inlet, which has an adjacent circuit breaker. There are four areas, each for a single channel, each having controls and connectors as follows. The input is a 3-pole, detachable, terminal connectors; Euroblock or 'Pheonix' style. The level control is recessed and screwdriver-operated. A larger 3-pole Euroblock connector provides the connection for remote level control. A switch switches the hi-pass filter in and out of circuit. The controls for channel 2 and channel 4 also have bridge switches, connecting channels 2 and four to channels 1 and 3 respectively. Channels 2 and 3 also have a switch to select the input from channel 1, rather than channels 2 and 3, so that all three could be driven from a single input. Channel four offers the choice of the channel-2 input or the channel-4 input. Two 4-pole Euroblock connectors provide the loudspeaker connections. A blanking panel covers the aperture where the optional VTX-WM1 Web Monitor Card may be fitted.

Inputs: 0.775V RMS, 0dBu, for maximum output, 10k ohms, balanced. Filter: -3dB at 65Hz, 18dB/octave, switched. Maximum VCA attenuation: Better than 90dB. Response: 20Hz - 20kHz, +0/-1dB, with filter bypassed. Distortion: 0.03% THD+N, 1kHz, 1W, 4 ohms load. Noise: Better than 100dB below full output power, 20Hz - 20kHz; 103dB 'A' weighted. Crosstalk: -90dB, 1kHz; -70dB, 10kHz. Power source: 230V AC, +/-10%. Dimensions: 482.6 x 88 x 451(w x h x d)mm, 2U rack mounting, 451 depth including connectors.

Model Power output (1) Bridged power output (2) Weight
VTX4120 4x 120W 2x 240W 15.8kg
VTX4240 4x 240W 2x 480W 18.5kg
VTX4400 4x 400W 2x 800W 22.1kg

Notes: (1) Normal mode, continuous sine wave, 4 ohms load, all channels driven. (2) Two pairs of bridged channels, each with 8 ohm load.

Included accessories: AC power lead, Set of mating screw-terminal connectors, push-in feet, manual.
Optional accessories: The WM-1 surveillance card allows remote monitoring of the amplifier's performance and settings from any computer via a standard web browser, see Cloud Web Monitor Cards - VTX Series. The RL-1remote control plate fits a standard single-gang UK back-box and gives control of the level of one channel using screened 2-core cable up to 100 metres long. The CXL-100T line driver transformer is suitable for use with one channel of the VTX4120 to provide a 100V or 70V line output, see Cloud 100 Volt Line Transformers.

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CLOUD VTX4120 POWER AMPLIFIER 4x 120W/4, balanced inputs, optional web monitoring   Stock code: 93-0701
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CLOUD VTX4240 POWER AMPLIFIER 4x 240W/4, balanced inputs, optional web monitoring   Stock code: 93-0702
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CLOUD VTX4400 POWER AMPLIFIER 4x 400W/4, balanced inputs, optional web monitoring   Stock code: 93-0703
No longer manufactured. Unfortunately we are not currently able to offer an alternative.