M490J — Mic Input Module

M490J MIc NPUT MODULE The M49OJ provides comp ete microphone channel facilities inclusive slide mixing attenuator source ector and mixing bus assignment switches as required for mixing consol input 4' ` ' Input and Preamplifier The mutually interlockea INPuT SELECTOR switches SW1 anc Sw2 allow the selection one two available microphone sources An adit- iona contact 5 supplied for control purposes each switch.

The impedance presented by the input transformer substantially higher than the nominal source impedance 150 ohms Tne Second- ary connected the preamplifier consisting through 07 and 21 Input sensc itivity the module may be varied by adjustment the SENSITIViTY control R25 covering range dB _ The balanced eamplifier ouiput appears module connector P2, pins 6/F 49' ' ~T = s 6 -.

'M1 | Inserts . 7 Two series-connected balanced insert points are made available P2 pins 6/F 8/J, 5/E and 7/HJ operating nomina level dBm _ They allow the insertion encillary processing equipmen into the mixing channel signal path such as compressor equalizer ter The provision two series connector insert points ermits the utilization the module stereo systems such as the WBS model R1200/R2o00 consoles these and similar applications the functions ssociated with the left and right Insertion Selectors (M499) may both be inserted into the channel with the left channel insert function preceding the right channel function So:: ` n ~j ' ' 0 ' _ .

. . Attenuater From the insert points, the signa routed ATtI balanced slide attenuator featuring continuous mixing range more than dB prior cutoff_ The CUE channel feed taken from the input side the attenuator '~'^ ' .a = |

M490J Mic INPUI_MODULE This change state can be brought about Dy any one three different methods: Momentary operation the CUE switch Sw12 (0) Momentary ground losure the EXTERNAL CUE control input P2 , pin Operation the "overpress switch SWi1, located the slide attenuator beyond the infinite" position. The ON status the CUE channe driven by 011 indicated by 052, wnich Cue off An additional Teature ensures that the CUE channel wili Iways switch OFF whenever the slide attenuator moved onto way from the "infinite" position regardless its prior state.

The control signal for this action initiated by the change state the ATTENUATOR cut switch Swio. The resultant Ievel change being either positive negative going processed through 27 29 and 210. The output produced pin 21o wili always be negative going pulse approximately 500 milliseconds duration. CRI2 Passes this pulse 28_ Pin thereby clearing' the B-section the flip-flop and resulting pin 28 switch Fema a[) volts turn switching the CUE switch OFF AII logic control inputs are bufiered and switch bounce guard against spurious noise Power_Supely Decoueling Power supply decoupling provided by R1L6 R149 and C5o C53 CR16 and CRI7 serve prevent amplifier damage the event supply voltage reversa The decoupling network drops the +/-25 volt supply rails nominal voltage +/-18 volts.

015 decouples and filters the positive suppiy rail, resuli ting an output +12 volts operate the cmoS circuitry additon, 23 and 24 are further decoupled by R54 R55 , C21 and C22