Audio Developments AD149 - Manual (Page 26)

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however, a more important rôle: no longer do we have to tolerate the mixer output
being limited because of the output from a particular microphone; the microphone
can now be controlled at source. Odd/even pairs of microphone/line input modules
may have their limiters linked for stereo operation by a DIL switch on the mother
board - and situated between the relevant pair of modules.
Past technical limitations have been responsible for these less-than-perfect ways of
operating. Once upon a time, it was possible to achieve a gain swing of only 30dB in
the input stage, necessitating the introduction of a 20dB attenuator (pad) - thus
degrading the signal-to-noise ratio - to enable the amplifier to accept the full voltage
range from a typical microphone.
Now it is possible to produce a virtually overload-proof input stage in which a pad is
redundant, and an external attenuator required only on very rare occasions. With
such an amplifier, the gain control element can be placed in the ideal position, ie the
feedback loop, ensuring the best possible noise performance.
...we have just described AD149's microphone amplifier.
Any audio-mixing system is, inevitably, and at all stages, a compromise between
headroom, signal-to-noise ratio, dynamic range, sensitivity.
We believe that we have achieved the state of SHIBUI.
Some boom-microphone operators dislike wearing combination headsets, preferring
to use the boom microphone itself for talkback purposes. In this case, privacy is
essential between boom operator and sound operator. Once a module has been
assigned to the boom microphone, an internal DIL switch will guarantee the required
privacy - a private line. This is a feature also available to a boom operator wearing
the standard headset when a guaranteed private conversation between boom and
mixer is required.
By a second internal DIL switch, the boom microphone may be routed to the
monitoring section for audition, in isolation, by external 1 and/or external 2, without
interfering with the sound-mixer's requirements.
For a mixer of its type and size, AD149 has an ultra-sophisticated auxiliary section.
When sourced post fader and with level controls at maximum, auxiliary signals are at
the same level as, and track with the main L/R output from the module and are
controlled by the channel fader. In this case, auxiliary outputs are available even
when the L/R output is switched off. It is normal practice for auxiliary level controls to
act only as attenuators, but when sourced pre-fader, an extra 10dB gain is introduced
into the auxiliary paths. (We believe this to be unique to AD149.)
An auxiliary stereo link converts auxiliary 1 level-control into a master control for both
paths, and auxiliary 2 level-control into a panpot across the auxiliary outputs from the
module.