High-pass filter
This switch activates the high-pass filter (often also called a “rumble filter”), which operates
from 50 Hz downwards with 12 dB/octave. The filter prevents the amplification of unwanted
low frequencies. Compared to 6 dB/octave filters, the 12 dB filter works more intensively, thus
more effectively – therefore the threshold is set to a low 50 Hz.
INSTR./LINE GAIN
This control determines the level of preamplification for signals connected either to the rear
LINE IN or to the INSTRUMENT input on the front. You activate the respective input with the
INSTR./LINE IN switch which is described below.
Gain range for line signals reaches from -12 dB to +22 dB. The attenuation allows to also
process very high levels. The 0 dB mark is highlighted in the line gain scale – this facilitates
to find the setting where a line level signal is processed at unity gain.
Instrument signals can be amplified b4 dB and +39 dB.
INSTR./LINE IN
With this switch you select between the microphone (off) and line or instrument inputs (on).
The rear mic and line inputs can remain connected, regardless of which input is selected. You
can choose the line input as source as long as the instrument input is not being used.
INSTRUMENT
The INSTRUMENT input jack is placed on the front for easy access. It should be used to connect
instruments like e-bass and guitars, acoustic guitars with pick-ups, etc. The INSTRUMENT
input features a 1 MOhm (one mega Ohm) input impedance. Line signals with lower imped-
ances, such as from D/A converters, samplers, synths, etc. should be connected to the rear
LINE IN socket.
IMPORTANT: As long as an instrument is plugged into front INSTRUMENT input, the rear
panel LINE IN input is deactivated.
Gain adjustments
For perfect levelling of the preamplifier firstly switch off all other modules (de-esser,
compressor, 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 +3 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 gain value is to be
reduced accordingly.
12
Channel One
Preamplifier
Control Elements
