Sound Performance Lab 9523 - Manual (Page 6)

6
Control Elements
The preamplifier stage of the M IKE M AN is based on the SSM 2017
semiconductor. The strengths of this particular component are its
extremely low noise and distortion characteristics. Unlike discre-
tely designed circuits, the SSM 2017 has 64 transistor functions
(discretely up to 24), thus achieving a very high common mode
rejection.
Preamplification of the input signal is determined by the MIC
GAIN control. The control range of the preamplification values
ranges from +22 dB to +72 dB. The maximum amplification value
specified is a minimum value. The preamplifier stage provides up
to +75 dB. This value can be lower, depending on the tolerance of
the potentiometer, but it never falls below a value of +72 dB.
The maximum input level is +25,7 dB! This high input capability
reduces the need of limiting.
When setting the MIC GAIN value, take note of the transducer
type (condensor or dynamic microphone) and the free-field
transmission factor of the microphone type. The sound pressure
level of the sound source to be recorded, the distance to the
microphone and the room acoustics are other factors which also
have to be taken into account when setting the MIC GAIN poten-
tiometer. The free-field transmission factor of a dynamic micro-
phone is around 2 mV/Pa, that of a condensor microphone can be
up to 20 mV/Pa, which equals an increase in the output level of
20 dB.
Pressing the phase switch (PHASE REVERSE) inverts the polarity
of the microphone signal. When the switch has not been pressed
(status LED is off ), the polarity is »in phase«. Pressing the switch
means that the polarity is »out of phase«.
Phase inversion can be used for a number of different reasons:
1. If, for example, the microphone signal of a singer or speaker is
preamplified in the M IKE M AN and the monitor signal is folded back
to the headphones, the singer or speaker cannot hear himself
very well. Pressing the phase switch inverts the polarity of the
microphone and consequently, of the headphone signal, and the
singer or speaker can then hear himself on his headphones
without having to increase the level.
Mic Gain
2
1
Phase Reverse
1 2
5
3 4