Instruction Manual

The Microphone/Line input module functions are as follows: Switch (12) selects 48V

phantom and 12V tonader power for condenser microphones. Powering may be

selected before or after connecting the microphone, but switch off all powering on

unterminated modules to ensure unconditional stability of the mixer. For complete

safety of external equipment, switch off microphone power before connecting a line-

level signal.

Phase change (15) is pre transformer and operates on microphone and line inputs.

∅

is the normal position.

The switched high-pass filter (14) is pre transformer and, similarly, operates on

microphone and line inputs. In this position the filter protects the transformer from low-

frequency saturation caused by wind, traffic, air conditioning etc. Operating

frequencies are to be found in the TECHNICAL SPECIFICATION. The high-pass filter

operates independently of the equaliser.

A continuously variable high-pass filter (2) is also incorporated and follows the

microphone pre-amplifier stage. This enables other troublesome low frequencies to be

attenuated and being variable can be adjusted to the optimum frequency and thus

minimising the effect on the required audio signal. This high-pass filter also acts

independently of the equaliser.

The input gain of the microphone amplifier is set by the rotary potentiometer (1) The

range of this control is 45dB. For line level signals, an input attenuator (30dB) is

inserted via switch (13); the MIC/LINE change-over switch.

To control the gain of the input amplifier a limiter may be introduced into circuit using

toggle switch (22) – limiting action being indicated by an LED (10). Factory settings of

the limiter can be found in the TECHNICAL SPECIFICATION. An internal preset

potentiometer allows a different threshold level to be set, but should be done with

great care. (An extender module is required if this adjustment is needed). Despite the

presence of the limiter around the input amplifier overload can still occur in later

stages. The limiter operates on both microphone and line level signals.

Following the microphone amplifier is the simple, but effective, equaliser which has

been retained from the original PICO - selector switch (19). Because of the inherent

inaccuracy of the centre-detent mechanism, it is not Audio Developments’ practice to

fit such devices to equaliser amplitude controls - HF (16), MF (17), LF (18). The three

equaliser controls have a mechanical push mechanism enabling them to be locked

away after setting, thus avoiding accidental adjustment.

The auxiliary section is incorporated below the equaliser controls. The two auxiliaries

are independent of each other; each has its own off/pre/post switch (20) and (21). The

off position disconnects the channel signal from the auxiliary busses and the pre/post

position routes the signal to the busses from either the pre or post fader position of

the signal path. The auxiliary routeing switches are independent of the channel L/R

routeing.