Microprocessor controlled microphone and line amplifiers with automatic gain control, designed for use in situations where technically skilled staff may not be available to set levels, such as remote contribution studios and workstations, or where automatic gain setting offers operational advantages such as with camera-sited microphones or talkback systems. Two models are now offered, one with simple remote control and or balanced to unbalanced converter circuit and another with a switchable mono/stereo headphone amplifier, ideal for driving PC type active loudspeakers.
Operation is extremely simple: The user presses the 'Take' button, which flashes until audio signal is applied to the input. The signal is sampled for six seconds, the system automatically selects between microphone and line mode and adjusts gain to provide a 0dbu output; the light remaining illuminated to indicate the sampling is in process. The settings are then saved in non-volatile storage until until the 'Take' button is pressed again.
Occasional peaks in level are controlled by a compressor/limiter in the output circuit that compresses signals above +4dBu, at a ratio of 2:1 and limits at +8dBu. The limiter is capable of applying 10dB of limiting without compromising the noise and distortion performance achieved at normal operating level. In addition, to assist with short-term level variations, progressive gain reduction of up to 8dB is applied when limiting is detected, which is then restored over a period of 20 seconds when the limiting ceases.
The front panel has the 'Take' button, a switch to activate phantom power (48V) which can be toggled or locked on and off, three LED indicators to show compressor, limiter, and gain reduction status in normal conditions, and the gain range in which the system is working whilst the gain reduction phase initiated. The rear panel has a 2.5mm co-axial socket for the external power input, a male, 9-pin d-sub connector offering simple remote control of the 'Take' switch contacts and LED, remote power (+5V max 20mA, +/-12V or PSU), mute and un-balanced output, and XLR-3 connectors for input and output. Both of the latter are electronically balanced.
Input level: -80dBu to +20dBu; impedance: 1kohms, mic; 10kohms, line. Noise: Less than -83dBu peak at 0dB gain, Distortion: Better than 0.02% at +10dBu. Output impedance: 50ohms. Power source: 12-24V DC, 4W maximum. 2.5mm barrel, centre positive. Dimensions: 94 x 52 x 108 (w x h x d)mm. Weight: 250g.
Included accessories: Instructions
Optional accessories: See BCD RACK MOUNTING PANELS - Extruded box for details of rack mounting-options and see CANFORD EXTRUDED BOXES MOUNTING KITS.
ALT-2S
Also the same as the ALT-1 but includes a circuit which can be a mono/stereo headphone amplifier. Useful for driving active PC style loudspeakers. A miniature jack connector gives access to the headphone output. Stereo line input on 5-pin XLR accompanies the standard 3-pin XLR input and output.