AIV Germanium One Einbauanleitung Und Betriebsanleitung Seite 32

If the distortion continues, proceed as follows:
Clamp the negative conductors (–) at Point 1 of the audio system and attach to engine block.
Check to see if the problem has been repaired.
If the engine block does not repair the problem, the auto body must be scanned, while the engine is
running, with the negative conductor of the system until a clear reduction in distortion occurs.
Free this point (= Point 2) and remove remaining underneath protection.
Place screw with a large diameter on this point. Clear the area on the auto body around the screw
and protect with auto body grease.
Attach all grounding cables or set multiplier on this screw and run to all devices. (central ground).
Any remaining distortion can be corrected with an LC-filter in the positive cable.
A millivolt meter (smallest voltage drop) or milliohm meter (slightest resistance) can also be used to
determine the central ground. The engine block or Point 1 should always be the point of reference.
Digital electronics in the vehicle cause an audible distortion up to the GHz range (interference from
wireless reception and car telephones). The switching power supplies of the amplifiers, digital tuner, and
CD-radio likewise contribute heavily to the current contamination. All of the distortion spectra appear in
the supply lines and are partially processed in the amplifier output stage. This results in a veiled sound in
the high tone range. Output is already heated in the no-load operation or in the smallest capacity range
by high-frequency distortion. The preliminary input stage of the amplifier cannot differentiate between
music and distortion and therefore faithfully amplifies everything that presents itself at the „pre-in"/or
current input. In order to dampen this effect, the optimum is realized at the output stage during the
manufacturing process. This is documented by the EU type approval, whereby test specimens are
examined for irradiating distortion and for self-produced distortion. Only after adherence to the EMD limit
values is an E-No. assigned. For the reasons mentioned, the frequency range of the output stage should
drop at the last after 50 kHz in order to avoid unnecessary heating. With output stages in Class A or
preamplifiers in Class A higher bias current in the low capacity range makes heating up unavoidable and
should not be confused with the described influence of distortion.
The removal of the distortion can only be accomplished through specific measures and requires
extensive expertise in the area of filtering technology for proper installation of the system. Important and
useful suggestions regarding this can be found in the relevant technical literature. Attention to the basic
rules for laying cables, central grounding and filtering of the current feed allows a good basic filtering to
be presupposed based on use of qualitative cinch cable. Special screening problems, which can vary
depending upon vehicle type, must be repaired according to each individual case directly by the
particular specialist.
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