SoundCraft MPM 20/2 - Manual (Page 8)

8
WIRING UP
Mic Input
The MIC input accepts XLR-type connectors and is designed to suit a wide
range of BALANCED or UNBALANCED low-level signals, whether from deli-
cate vocals requiring the best low-noise performance, or drum kits needing
maximum headroom. Professional dynamic, condenser or ribbon mics are
best because these will be LOW IMPEDANCE. While you can use low-cost
HIGH IMPEDANCE mics, you do not get the same degree of immunity to
interference on the microphone cable and as a result the level of back-
ground noise may be higher. If you turn the PHANTOM POWER on, the socket
provides a suitable powering voltage for professional condenser mics.
The input level is set using the input GAIN knob.
The LINE input offers the same gain range as the MIC input, but at a higher
input impedance, and is 20dB less sensitive. This is suitable for most line
level sources.
Line Input
Accepts 3-pole 6.35mm (1/4") jacks, or 2-pole mono jacks which will auto-
matically ground the ‘cold’ input. Use this input for sources other than mics,
such as keyboards, drum machines, synths, tape machines or DI boxes. The
input is BALANCED for low noise and immunity from interference, but you
can use UNBALANCED sources by wiring up the jacks as shown, although
you should then keep cable lengths as short as possible to minimise inter-
ference pick-up on the cable. Note that the ring must be grounded if the
source is unbalanced. Set the input level using the GAIN knob, starting with
the knob turned fully anticlockwise. Unplug any MIC connection when using
the LINE input.
Insert Point
The unbalanced, pre-EQ insert point is a break in the channel signal path,
allowing limiters, compressors, special EQ or other signal processing units
to be added in the signal path. The Insert is a 3-pole 6.35mm (1/4") jack
socket which is normally bypassed. When a jack is inserted, the signal path
is broken, just before the EQ section.
The signal from the channel appears on the TIP of the plug and is returned
on the RING, with the sleeve as a common ground.
The Send may be tapped off as an alternative pre-fade, pre-EQ direct output
if required, using a lead with tip and ring shorted together so that the signal
path is not interrupted.
WARNING !
Start with the input GAIN knob turned fully anticlockwise when
plugging high level sources into the LINE input to avoid
overloading the input channel or giving you a very load surprise!
DO NOT use UNBALANCED sources with the phantom power
switched on. The voltage on pins 2 & 3 of the XLR connector may
cause serious damage. BALANCED dynamic mics may normally be
used with phantom power switched on (contact your microphone
manufacturer for guidance)