Audio Developments AD255 Portable Mixer
AD255 is the latest 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 aluminum case with a relatively
The features and specifications are based on the well-established AD245 Pico
Mixer. Two auxiliary sends and channel direct outputs are the main additional
features. As with the other models within the range, professional components
are used throughout, including Penny and Giles 100mm long-stroke, conductive
Location sound professionals now require multi-track record facilities. The
channel direct outputs provide the necessary features without compromising the
simplicity of operation and reliability of its counterpart, the AD245.
- 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 equalizer, 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 high-pass filter protects against low-frequency saturation.
- The main stereo output is transformer balanced and has separate left and
- 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
- Limiters, which may be linked for stereo operation, are incorporated in
the main output. Limiting is indicated by a pair of LEDs.
- Input direct outputs are unbalanced and driven from a very low impedance
source with high drive capability.
- Two LCD meters display - either PPM or VU - monitor the main output, auxiliary
output and PFL of each input. Useful for monitoring levels 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
10 KHz, its output replacing the signal on the main output.
- Via an internal microphone, the mixer operator is able to communicate with
the main output (SLATE) and with an outstation (EXT). The outstation normally
receives a mono of the mixer's main output.
- The headphone monitor may be selected between main output, auxiliary outputs
and return 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 MS 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.
- The mixer receives power from 8 X C cells fitted internally or from an external
|Max Input Level
||Mic @ Max Gain -44dB @ Min Gain + 6dB
Line @ Max Gain -14dB @ Min Gain +20dB
TB Return +18dB
TB Return >20kR
||48v Phantom, 12V Tonader
||0: -1dB L-R & Mono
0: -1.5dB Monitor Paths
||HF: 10dB @ 10kHz
LF: 10dB @ 100Hz
Centre Frequency 2k5Hz Q=1.2
HPF: Pre-Transformer 12dB/Octave
-3dB @ 150Hz
-3dB @ 90Hz
||<0.05% @ 1kHz @ 0dBm Output
<0.15% @ 40Hz to 15kHz @ +15dBm Output
||<-70dB 40Hz to 15kHz
Intergroup & Interchannel
|| <60R L-R & Mono
<20R Direct Out & Monitor
<20R TB Send
|| +23dBm L-R Transformer Bal (600R Load)
Mono Transformer Bal (600R Load)
+18dBm Direct Out Unbalanced (600R Load)
Headphone Unbalanced (600R Load)
TB Send Unbalanced (600R Load)
||Mic <-126dB EIN 20Hz to 20kHz; 200R Source
Line <77dB SNR 20Hz to 20kHz 0dBu In & Out
Attack 2 Settings Internally Switchable
1: 4mS 2: 0.8mS
Release 2 Settings Internally Switchable
1: 250mS 2: 80mS
Factory Setting: Slow
||Illuminates @ +15dBu at the Pre-Fader Point
||220mA (6 input)
12V DC Supply
|Dimensions (excluding handle)
x 304mm x 120mm
AD255 Manual (pdf)