Adjusting ”Off” Attenuation
In instances when the number of microphones in use is high, it may be necessary to increase the amount of “off ” attenuation per microphone to keep the total ambient noise level low. There are “off ” attenuation adjustments inside the unit. To adjust the “off ” attenuation of channel 1, unplug the unit, remove the top cover and locate the trimpot designated on the circuit board by “VR3” (Figs. 4 and 5, page 11). It is factory set at approximately 8 dB, the attenuation at the middle of the control’s rotation. When the control is turned fully counter- clockwise, “off ” attenuation is approximately 20 dB. Conversely, when the adjustment is turned fully clockwise, “off ” attenuation is approximately 6 dB. VR6, VR9 and VR12 control “off ” attenuation for channels 2, 3 and 4 respectively.
Changing the settings of the switches designated on the circuit board by “SW5,” “SW11,” “SW17” and SW23” will extend the range of “off ” attenuation to
Preamp Outputs
Each microphone channel has an independent unbalanced preamp output that is separate from the main mixer output. This is helpful when it is necessary to record the output of each channel, whether or not it is the active mixer output (as is required, for example, in some courtroom proceedings). As set at the factory, no gating is applied to these outputs. To gate these outputs, unplug the unit, remove the top cover and locate the switches designated on the circuit board by “SW6,” “SW12,” “SW18” and SW24” (Figs. 4 and 5, page 11). Change the switch position(s) to “Gating” for channels 1, 2, 3 and/or 4 respectively, as desired.
Input Limiters
Independent, adjustable limiters are available on all mic channels. To adjust the limiter threshold of channel 1, unplug the unit, remove the top cover and locate the trimpot designated on the circuit board by “VR2” (Figs. 4 and 5, page 11). It is factory set at approximately 0 dB RMS. When the control is turned fully
is approximately +10 dB RMS. VR5, VR8 and VR11 adjust limiter threshold for channels 2, 3 and 4 respectively.
Changing the settings of the switches designated on the circuit board by “SW4,” “SW10,” “SW16” and SW22” will turn off the
Force-on/Force-off
To activate
External Control Connector Pinout
Pin 1 | Channel 1 force off | Pin 8 | Channel 4 force on |
Pin 2 | Channel 2 force off | Pin 9 | Channel 1 TTL out |
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Pin 3 | Channel 3 force off | Pin 10 | Channel 2 TTL out |
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Pin 4 | Channel 4 force off | Pin 13 | Ground reference |
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Pin 5 | Channel 1 force on | Pin 14 | Channel 3 TTL out |
Pin 6 | Channel 2 force on | Pin 15 | Channel 4 TTL out |
Pin 7 | Channel 3 force on |
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