SPL 9945, User Manual

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10
Operation
Pre-amplifier
Highpass
The Highpass filter is used to eliminate disturbing low frequencies. These
disturbances could impair the following processing or AD conversion. The
cut-off frequency at 50 Hz avoids influences to vocals. The roll-off is
12 dB/octave.
Instrument Gain
The Instrument Gain control determines the preamplification of the inputs
Line and Instrument. The signals can be preamplified from + 5 dB up to + 42
dB. By making use of the balanced line input the amplification is reduced by
about 18 dB to enable even very ”loud” signals to be processed. For further
information please read the next section “About levelling”.
About levelling
For perfect levelling of the preamplifier firstly switch off all other modules
(De-esser, Compressor/Limiter, EQ) and set the Output control to 0 dB. The
signal can now be levelled with the assistance of the PPM output display. To
achieve a good working level the values should range between 0 and +6 dB.
At these levels an optimal drive level
and enough headroom for further
processing (e. g. adding level in the EQ stage) is guaranteed.The Clip LED will
warn you of potential peaks; if during recording the Clip LED illuminates, the
preamplifying value is to be reduced accordingly.
Instrument/Line On – Mic Off
This button allows selection of the input source. The microphone signal is
available for processing when the button is not pressed; when pressed the
Instrument/Line signal is activated. As long as the Instrument Input at the
front of the unit is not in use the Line signal option on the back of the unit is
automatically available.
Instrument Input
The Instrument Input on the front of the unit is designed for the connection
of electric as well as acoustic guitars with their own pick up etc. This input is
of high impedance and designed for high amplifications. It is possible to
connect instruments with line levels, such as keyboards, samplers, drum
machines to the ”Instrument Input” to permit these to be processed quickly
with the Channel One, however it is preferable to connect line level equip-
ment to the ”Line Input” at the back of the unit, ideally via a patch bay. Line
Input provides a more stable level (see section ”Instrument Gain”) while the
connection via a patch bay offers the most flexible routing method
combined with the advantage of insensitivity to disturbance characteristic
of balanced wiring.