SoundCraft 1620LE - Manual (Page 27)

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MICROPHONE INPUT ON AUX 1, 2 AND/OR 3
Auxiliary inputs 1, 2, and 3 may be optionally equipped with Part No. 1620-MC microphone preamplifier cards and therefore use the
XLR connectors on the rear connector panel.
To install a connector and preamplifier card:
1) Remove the three screws fastening the top cover of the 1620LE to the chassis, and remove the cover.
2) Locate the selector switch to the left of the connector on the motherboard into which the new preamplifier card will be installed.
This switch allows its AUX input to be used as a line input when no preamplifier is installed, and must be switched over when the
preamplifier card is installed.
3) Install Part No. 1620-MC preamplifier cards in the required location(s) on the mother board. Note the orientation of the card
and make certain that the card correctly mates with the connector on the motherboard.
4) If required, adjust the gain of the preamplifier by rotating the trimmer on the top edge of the card. See the section on
Microphone Gain Adjustment.
5) Reinstall the top cover, using all seven screws.
6) Connect a microphone to the XLR connector, following the same wiring convention as for the other microphone(s) used with
the 1620LE.
WARNING: When the 1620LE has been modified as above, the RCA-phono sockets are still active. Do not
connect a line level input to these sockets, since the preamplifier will be severely overloaded and heavy
distortion will result. Additionally, if a microphone is simultaneously connected in parallel with a line input,
which could happen if the RCA-phono sockets are accidentally used at the same time as the XLR connector,
the microphone could be seriously damaged.