Design and Manufacturers of Professional Sound Mixers

AD256 is another addition to the Audio Developments Ltd range of portable mixers, having comprehensive facilities set out in an ergonomically friendly design and all contained within a robust and rugged aluminium case with a relatively small footprint.

The features and specification are based on the well established AD255 Mixer. Input channel limiter, continuously variable HPF and mute switch are the main additions. As with the other models within the range, professional components are used throughout - including Penny and Giles 100mm, long-stroke, conductive plastics faders.

Location sound professionals now require multi-track record facilities; the channel direct outputs provide the necessary features. By use of an additional switch these outputs can source other signals if the direct signal is not required, (Main Output and Auxiliaries). This without compromising the simplicity of operation and reliability as with its counterpart the AD255.

Low noise microphone amplifier developed for AD140 series of mixers. Power is provided for 48V Phantom and 12V Tonader microphones

A simple but effective three band equaliser, proved and approved under field conditions, in use throughout the AD140 series of mixers

Inputs are transformer balanced and protected against radio-frequency interference. A switched high-pass filter protects against low-frequency saturation.

An additional continuously variable high-pass filter with a range 20Hz to 250Hz.

The main stereo output is transformer balanced and has separate left and right faders

A mono output of the main left and right is also transformer balanced

.

Two auxiliary outputs are transformer balanced and have separate master rotary controls. Auxiliary 1 & 2 are routed from each input using a 3 position switch (off, pre and post fader). Auxiliary 2 has a rotary level control

Limiters are incorporated on both the inputs and outputs. The main output limiter can be linked for stereo operation. LEDs indicate limiting action.

Direct outputs from each input are unbalanced and driven from a very low impedance source with high drive capability and minimising line interferrence. As well as the channel signal, main and auxiliary outputs can be fed to this output; selected using a six position rotary switch

Two LCD meters display - either PPM or VU - monitor the main output, auxiliary output and PFL of each input. Useful for monitoring level at a direct output. Battery level and monitor status (Direct or Return) are also indicated. Meters can be illuminated.

The frequency of the internal oscillator can be selected between 1KHz and 10KHz, it's output replacing the signal on the main output.

(SLATE) auAn internal microphone enables the mixer operator to communicate with the main output xiliaries and an outstation (EXT) . The outstation receives a monitor signal selected using a series of five push-switches. Left, Right, Aux 1, Aux 2 and Boom

The headphone monitor may be switched between main output, auxiliary outputs and returns. All have PFL override. Monitor selectors allow left , right, left + right, auxiliary 1, auxiliary 2 and auxiliary 1 + 2 to be routed to the headphone socket. An M-S matrix amplifier may be inserted in order to decode main or auxiliary outputs in the M-S domain.

An electronically balanced stereo tape return appears on a pair of stereo jack sockets. An input calibration potentiometer is adjacent to the jack sockets on the connector panel.

All input and output connectors are presented on one surface of the case and in line with their corresponding modules.

REFERENCE 0dB=775mV at 1kHz unless otherwise stated.

MAX GAIN

MIC 75dB

LINE 45dB

MAX INPUT LEVEL

MIC @ MAX GAIN -46dBu @ MIN GAIN -1dBu

LINE @ MAX GAIN -15dBu @ MIN GAIN+20dBu

STEREO-RETURN +18dBu

TB RETURN +18dBu

INPUT IMPEDANCE

MIC >2k2R

LINE >6k5R

STEREO-RETURN >100kR

TB RETURN >20kR

MIC POWERING

48V PHANTOM & 12V TONADER

MAX OUTPUT

+23dBm L-R, AUX & MONO

(600R LOAD) TRANSFORMER BAL

+18dBm DIRECT OUT, H'PHONE & EXT 1

(600R LOAD) UNBALANCED

OUTPUT IMPEDANCE

<60R L-R, AUX & MONO

<20R DIRECT OUT, MONITOR & EXT 1

FREQUENCY RESPONSE

0: -1dB L-R, AUX & MONO & DIRECT OUT

0: -1.5dB MONITOR PATHS 20Hz to 20KHz

HARMONIC DISTORTION

<0.05% @ 1kHz @ 0dBm OUTPUT

<0.15% @ 40Hz to 15kHz @ +15dBm OUTPUT

OVERLOAD INDICATOR

ILLUMINATES @ +15dBu at the PRE-FADER POINT

CROSSTALK

<-70dB 40Hz to 15kHz

INTERGROUP & INTERCHANNEL

NOISE

MIC <-125dB EIN 20Hz to 20kHz; 200R SOURCE

LINE <80dB SNR 20Hz to 20kHz 0dBu IN & OUT

EQUALISATION

HF: ±10dB @ 10kHz

LF: ±10dB @ 100Hz

MF: ±15dB

CENTRE FREQUENCY 2k5Hz Q=1.2

HIGH-PASS FILTER

SWITCHED PRE-TRANSFORMER -3dB @ 70Hz

VARIABLE POST-TRANSFORMER 20Hz to 250Hz

INPUT LIMITER

THRESHOLD +10dB FADER AT CAL

RATIO 10:1

ATTACK 2mS

RELEASE 200mS

OUTPUT LIMITER

THRESHOLD +8dB

RATIO 7:1

ATTACK 2 SETTINGS

INTERNAL SWITCH 1: 4mS 2: 0.8mS

RELEASE 2 SETTINGS

INTERNAL SWITCH 1: 250mS 2: 80mS

FACTORY SETTING: SLOW

CURRENT CONSUMPTION

350mA (6 INPUT)

12V DC SUPPLY

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