Important Notice - Audiotec Fischer helix Bedienungsanleitung

27 Adjustment of center frequencies
Control 27 can be used to select the frequency from 30-
120 Hz of the adjusted lowpass (control 23). this can be
enhanced with control 26 from 0 to 9 dB.
It is usefull to emphasize or correct a determined fre-
quency of the subwoofer (kickbass)
dB
variable
20 30 50 100 200 300 500
30 Hz
120 Hz
28 - 29 Mono/ stereo switch
To set the operating mode of the amplifier.
4-channel: If the amplifier operates in 4-channel mode
both switches have to be set on stereo and position 1
3-channel: If the amplifier is operates in3-channel mode
(frontsystem/ subwoofer) set control 28 of channel A
and B for the frontsystem on stereo, position 1 and con-
trol 29 of channel C and D on mono, position 2.
Caution: Channel C and D must be bridged in 3-
channel mode operation, because channel A and B
can only be bridged in 2-channel mode. It ensures
that channel C and D are used as mono channel for
the subwoofer. Only this channels have bassboost.
Both inputs 9 and 10 must be used for bridged channel
because both channels operate the summation signal. If
there is only one mono signal for the subwoofer the sig-
nal must be distributed on both inputs with switch 6 or
use a Y-adapter.
2-channel: If the amplifier operates in 2-channel mode
set control 28 of channel A and B and switch 29 of
channel C and D on mono, position 2.
8
Caution: Bridge at first channel C and D before you
switch to 2-channel mode. If channel A and B cannot
be bridged make sure that control 29 of channel C
and D is set on position 2 (mono). Only input A and B
have to be used in 2-channel mode. Thus the signal of
input A is used for the bridged channel A and B and the
signal of input B for the bridged channel C and D.
30 Full active operating mode
With the use of control 30 the amplifier is operating in
full active mode. Set the switch on position 2. In this
case the frequencies of input A and B (only this can be
used in full active mode) are set for channel A and B.
Hz
The lowpass of the signal's adjusted frequency with con-
trol 22 for channel A and B will be transmitted to chan-
nel C and D, regardless of switch 18 position (HP/ Lin/
TP), no matter if channel A and B are used as highpass,
full range or lowpass, the signal is always transmitted
as lowpass to channel C and D. Adjust the desired fre-
quency of the transmitted signal with control 22. Due to
the transmission of lowpass to channel C and D it is pos-
sible to build a bandpass with a bandwidth of 15 Hz up
to 7 kHz.
variable
2K
15 Hz
Example 1: When channel A and B are operating in full
range channel C and D have the lowpass frequencies set
with control 22.
Example 2: When channel A and B are running as high-
pass 2 kHz, the frequencies up to 2 kHz are for channel
C and D. If you turn to highpass i.e. 80 Hz you get a
bandpass fro 80 Hz to 2 kHz for channel C and D.
Bandpass 80Hz to 2 kHz
80 Hz
31- 32 Level control for channel C and D in full active
operating mode
Adapt the output level of channel C and D with control
31 (channel C) and 32 (channel D) in full active opera-
ting mode to channel A and B. The control range of each
channel is +/- 6 dB.
In 3-channel mode (mono C/D) both controls (31/32)
have to be used.
In 2 channel mode these controls are not activated.
Caution! To avoid a lost of sound pressure make sure
that the crossover frequencies of high-and lowpass
are separated of 2 Octave when building a bandpass
on channels C/D in full active mode.
That means: If the lowpass signal of channel A/B is
transmitted to channel C/D, the highpass of channel C/D
should be 2 Octave lower.
5K 10K Hz
Example: Lowpass tansmission 320 Hz - then highpass
7 kHz
crossover frequency adjustment on channel C/D = 80 Hz
(1 Octave = double frequency or halve frequency).

Important Notice:

The amplifier A4 Competition has a temperature con-
trolled innovative power supply.
This newly developed feature makes possible that the
amplifier reduces the output power at very high tempe-
rature. It protects the amplifier from destruction and
overheating shut off. This power reduction is not audible
in normal application because it only comes into affect
2K 5K Hz at high power peaks and when the amplifier gets very
hot due to high outside temperatures. If the amplifier
2 kHz shuts off due to overheating (> 95°C) it can take some
minutes until it turns on again.
Also due to the integrated safety electronic the amplifier
turns on with a delay of 3-4 seconds. This is because of
the internal check up of all relevant voltages that ensure
a perfect operation.
This amplifier has several electronic protection circuits
that shut off the amplifier at overheating, overloading,
short-circuit on loudspeaker, low-ohmic mode or defec-
tive power supply.
It is indicated through different LEDs (see CPS system
at point 15-17).
Please check for connecting failures such as short-cir-
cuits, wrong connections and over-temperature.
If the amplifier does not turn on it is defect and has to be
send to your local authorized dealer for repair service. A
detailed description of the malfunction and the purchase
receipt has to be attached.
Never connect the loudspeaker cables with the car
chassis gound. It damages your amplifier. Ensure that
the loudspeaker systems are correctly connected
(phase), i.e. plus to plus and minus to minus. The plus
pole is indicated on most speakers.
The A 4 is adjusted as 4-channel amplifier before ship-
ping.
In tri-mode operation channel C and D must be bridged
to mono. In most of the installations the bridged mono
channel due to the higher output power is used to run the
subwoofer and the bassboost is assigned to this chan-
nels.
In 2-channel operating mode channel A and B can only
be bridged when C and D are already bridged.