The AVC4 is fundamentally two AVC2s combined into a single 1RU 19 inch rack mount unit to provide sound level control with the least impact on the audio quality.

The AVC4 will control the maximum sound level of two stereo channels and there are two independant level settings for each stereo channel. The AVC4 automatically adjusts the volume once a preset threshold has been reached to keep the audio level within that required. When attenuating the audio signal the distortion from the AVC4 is less than 0.01% so the quality of the original audio is maintained. A single adjustment is all that is required to set the unit.

Once the control level is reached the AVC 4 starts to attenuate the audio, the amount of attenuation is indicated by the LED meter on the front panel (a compact remote display option is available). The more the sound input level is increased the more the AVC 4 will decrease it and there is a clip LED to indicate if the system is being overdriven. The AVC4 has provision for 2 different levels to be set and either level can be selected using a switch or timer. If for example a different setting is required for evenings or when doors are open.

There are also dim and mute facilities and if the system is to be linked to a fire alarm these connections will meet the requirements.

The AVC 4 will not instantly react to individual peaks or dips but responds to average programme level (this avoids sudden volume changes). The factory setting gives smooth operation that is almost imperceptible as the level is automatically adjusted, with minimal effect on your sytems audio quality. A security panel on the back protects against unauthorised adjustment.

Some advantages offered by the AVC4 over compressor / limiters are: No reduction in the dynamic range of the system under normal operating conditions so the music remains punchy without the restricted sound of compressor/limiters.

Compressor/limiters are a recording studio tool designed to restrict the dynamic range of a music signal, usually to make it easier to control and mix. When used in the studio, compressor / limiters have an array of controls to set attack and release times, threshold and compression ratios. In this case, the settings will be adjusted as required by the music, but without the controls used in studios the dynamics will be restricted and may not sound particularly musical. Consequently compressor limiters should not be used in music systems, however until the introduction of the AVC2 there were few options. Now the AVC4 offers greater control over the audio signal without compromising music quality and is probably the best product for controlling audio volume levels on the market today.

The AVC 4 offers great flexability with its different facilities, allowing the set up to be tailored to the individual installations requirements. The AVC4 has no external controls which means that tampering is minimised. The LED display and clip indicator provide all the information the operator requires. A choice of linear, A or C frequency weightings or a combination of both are available.


AVC4 Technical specification
Channels: 2 Independent Stereo channels
Frequency Response: 20Hz - 20Khz +/- 0.5 dB
Distortion:THD+Noise @ 1Khz O/P Level 0dBu <0.01%
Noise 20Hz - 20Khz: EIN < -90dBu
Inputs: Electronically balanced, connect negative to screen for unbalanced use.
Input impedance: Balanced 20K Ohms Unbalanced 10K Ohms
Maximum input level: +22dBu
Clip indicator: Indicates @ +20dBu
Outputs: Electronically balanced, connect negative to screen for unbalanced use.
Source impedance: 100 Ohms
Minimum load impedance: 600 Ohms
Operating Threshold Range: High range: Average level adjustable -2dBu to +6Bu Low range: Average level adjustable -14dBu to -6dBu
Attenuator Range: 0dB to -30dB
Control chain: The control chain has a flat frequency response or "A" weighting" or a combination of both. Other responses available on request.
Facilities: Mute, Dim and level 2 selection are via connections to the back panel. Mute or Dim can be used for fire alarm interfacing, the level 2 allows a different level to be set and selected either by switch or timer.
Power: 220V - 240V (Internally switchable to 110V). IEC Mains connector; mains fuse 250mA slow blow.
Finish: Front and Rear panels - Black anodised aluminium with silver legend. Case - Black plastic coated steel.
Dimensions: 19" Rack mounting, 1RU Width 482mm (19 inches) Depth 200mm (7.9 inches) Height 44mm (1.75 inches) 997