M406 — Compressor - Limiter

The M406 is designed to mount directly on console control panel and in line with a straight line mixing attenuator A cutout 6L_ X .S6W inches and two 4_ 40 tapped holes will be required (see dimensional outline drawing) The M406 escutcheon will overlap the cutout and holes Connections are made to the 14 pin female mating connector in accordance with drawing 406-09-001 and the following table: Function: Termination Input 150 ohms Strap A to D and C to F , connect to A and C Input 600 ohms Strap D to F connect to A and C Output 600 ohms P and R Common negative 48 volts B+ GND (chassis) Meter 6 and M POWER REQUIREMENTS: The M4O6 requires 48 volts dc regulated 1OOmA from an M648 , M548 or equivalent

PRELIMINARY_ CONTRQLS Threshold: Sets the level at which the M4O6B will begin to compress (-l2dBm to +8dBm) Note: Due to the difference between transient program material and sine- wave test signal compression is set to begin at level 4dB higher with sinewave test signal as indicated on the threshold control. Compression: Determines the slope or ratio of output level change for given input level change .

The slopes indicated are 2/1, 3/1 , 5/1. 10/1 and limit in the limit position, the slope is greater than 20/1, that is, 20dB increase on the input will permit only ldB increase at the output) VU / GR: This is small concentric knob atop the compre- ssion control_ This selects an external VU meter to indicate the output level of the compressor In the VU" position, it is calibrated to read "0" when the output level is OdBm .

In the GR position (gain reduction) the meter will read when compression begins the meter will deflect downward giving an indication in dB of the amount of compression or gain reduction being applied to the incoming signal. Recovery: Determines the rate at which the compressor recovers from its compressed condition, The control is labelled 1, 2 , 3 , 4 , 5 positions corresponding to 44 , 12 , 1, 3 & 5 seconds .

De-ess-: This is the small concentric knob atop the recovery control. The control is labelled 0 2 4 ,, 6 , 8 , which indicates in dB the amount of additional high frequency compression provided when the compression switch is set to the 2/1 slope. Note: The purpose of this is to help reduce sibalance sounds from persons voice and should be used only on the 2/1 compression slope with short recovery time position 1 or 2 ) Insert Pushbutton: Activates the compressor circuitry in the M4O6B The light next to the pushbutton will indicate this condition.

Note: The amplifier section of the compressor is not bypassed by operation of the insert pushbutton

The M406 has three groups of concentric controls to be used throughout the operation of the unit. These transient-free controls may be pre-set or adjusted during the operation of the unit. Upper Concentric_ groyp: Inner (small) knob: THRESHOLD This iS an input gain control designed to adjust the input level to the compressor and control amplifier . Since the compressor circuit always commences to compress at a specified level and introduces fixed degree of compression (depending on the slope 2/1, 3/1 , etc.), an input control must be provided to accommodate the variations of signal amplitude at the input _ The Threshold control provides this adjustment.

Note; If the Threshold control is reduced to zero (cCw) there will be no Signal output from the M406. Outer (large) knob: OUTPUT . This iS an output gain control designed to adjust the output level of the compressed program material to the required level of the system The Output control operates independently and does not affect the setting of the input control_ Note: If the Output control is reduced to zero (CCW) there will be no Signal output from the M406_ Centre Concentric group: Inner (small) knob: GR & VU SELECTOR This selector switch connects the external VU meter to the compressor electronics In the VU position the meter is connected to the amplifier output terminals to provide a VU indication of the outgoing compressed program material _ In the GR position the meter is transferred to the control amplifier to indicate the amount of gain reduction in db.

A subsidiary gain reduction scale is provided on the meter scale. Outer (large) knob: COMPRESSION _ The five position Compression selector determines the ratio of compression for the control amplifier. The options are 2/1 3/1 5/1 _ 10/1 and L (limit)