16
Initial start-up and functions
1
Optical Input (optional)
Optical inputs in SPDIF format for connecting signal
sources with a digital audio output. The sampling
rate of this input must be between 28 and 96 kHz.
Please note:
The digital inputs are not part of the
C FOURs standard equipment. These can only be
retrofitted with the optionally available HELIX Digital
Input Module HDM 2.
Important:
The signal of a digital audio source nor-
mally does not contain any information about the
volume level. Keep in mind that this will lead to full
level on the outputs of the HELIX C FOUR. This
may cause severe damage to your speakers. We
strongly recommend to only use volume controlled
audio sources!
Note:
This amplifier can only handle stereo input
signals and no MP3- or Dolby-coded digital audio
stream!
Note:
It is possible to use the
Optical Inputs
and the
lowlevel
Line Input
at the same time.
2
SPDIF Direct In switch (optional)
Due to the
SPDIF Direct In switches
, the input stag-
es of the individual channel pairs of the C FOUR
can be bypassed and the input signal of the
Optical
Inputs
directly and losslessly routed from the inte-
grated DA converter to the internal power stage. To
activate the direct signal routing you have to set the
SPDIF Direct In switch
to “On”.
Please note:
The
SPDIF Direct In
function is not
part of the C FOURs standard equipment. It is sole
-
ly included in the optionally available HELIX Digital
Input Module HDM 2.
Note:
These switches only affect the signal routing
of the respective
Optical Input
.
Note:
The appropriate channel pair of the amplifi
-
er must be operated in fullrange mode for routing
the digital input signal directly to the power stage.
Therefore change the position of the respective
X-Over switch
to “FULLRANGE“ (see page 18,
item 16).
Note:
If the switch is set to “On” position the lowlev
-
el
Line Input
(3) as well as the
Level controls
(10)
are without function!
3
Line Input
4-channel lowlevel line input to connect signal
sourc es such as head units / radios / DSPs.
4
GND
The ground cable should be connected to a common
ground reference point (this is located where the
negative terminal of the battery is grounded to the
metal body of the vehicle) or to a prepared metal lo
-
cation on the vehicle chassis i.e. an area which has
been cleaned of all paint residues. Recommended
cross section: min. 16 mm² / AWG 6.
5
+12 V
Connect the +12 V power cable to the positive ter
-
minal of the battery. Recommended cross section:
min. 16 mm² / AWG 6.
6
REM
The remote lead should be connected to the remote
output / automatic antenna (aerial positive) output
of the head unit / car radio. This is only activated
if the head unit / car radio is switched on. Thus the
amplifier is switched on and off together with the
head unit / car radio.
7
Output channels
Speaker outputs of the channels A - D to connect
speaker systems. The impedance per channel
must not be lower than 2 Ohms (4 Ohms in bridged
mode).
8
LPF
These controls are used to adjust the crossover
frequency of the lowpass filter of the channel pairs
A / B and C / D from 15 Hz to 4,000 Hz.
9
HPF
These controls are used to adjust the crossover
frequency of the highpass filter of the channel pairs
A / B and C / D from 15 Hz to 4,000 Hz.
