Sound Performance Lab 9523 manual Control Elements, Mic Gain Phase Reverse

Control Elements

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Mic Gain 1

Phase Reverse 2

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5

2 3 4

The preamplifier stage of the MIKEMAN 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 MIKEMAN 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.