SPL 9945, User Manual

Page: 9 / 28

9
Operation
Pre-amplifier
Microphone Gain
The Microphone Gain control determines the preamplification of the micro-
phone signal. The preamplification values extend up to + 65 dB. If Lundahl
input transformers are fitted the scale values are to be increased by + 14 dB.
Please refer to "About levelling" on page 10 for further information.
48 Volt phantom power
The 48 Volt phantom power in the Channel One serves to supply condenser
microphones which are equipped with in-built preamplifiers. A precise
construction and disturbance free electrical supply are the main require-
ments for their trouble free operation. In the Channel One the voltage is
maintained at a precise 48 V and delivers a maximum current of 14 mA. This
is sufficient for all types of microphones.
WARNING: All microphones with balanced, ground free output (including
tube microphones) can be operated with phantom power switched on. The
following procedure is to be adhered to: Firstly connect the microphone to
the Channel One, then switch on the phantom power – you can now
commence work. When recording has been completed firstly switch off the
phantom power then wait 30 seconds before disconnecting the micro-
phone from the Channel One.This allows residual voltages to be discharged.
Phantom powering is only used with condenser microphones. With any
other type of microphone it is to be switched off ! An unbalanced micro-
phone is not to be used with phantom power switched on!
Phase Reverse
The phase inversion function reverses the polarity of the microphone signal.
When the button is pressed the phase is rotated through 180º.The phase
inversion function is often useful, for instance to correct a headphone
monitor signal which is possibly wrongly phased. A singer/speaker can
actually hear himself during recording as well as over the headphones.
Incorrect polarity leads to an unnatural tone and to drastic tonal changes, if
the distance to the microphone is varied. We recommend that you check the
polarity and correct it if necessary before commencing recording.