and more often it is not possible to install radios ... - Herman Josip doo

Advice
Power supply
a) Power cable
he power supply is the most important point concerning the installation
Tof a car-hifi-system.
Using a sub-dimensioned power supply or wrong fuse values may not only
cause a loss in performance but you even risk that the car takes fire.
In fact, the amplifier is able to transform only half of the current taken from
the battery into performance. The other half of the current is – depending
on the construction – transformed into heat. We call it the efficiency of an
amplifier which ranges about 50 % in analogue types. Depending on the
quality it can be more or less.
The efficiency of a digital amplifier ranges about 75 %. This means that the
loss in power is less.
The following example explains how to choose
the right cable cross-section:
The total performance of an analogue amplifier is e. g. sinus 450 Watt
at 4 Ohm stereo. The average voltage in the car ranges about 13,8
Volt. You should consider the following calculation concerning the right
choice of the cable cross-section.
450 Watt/13,8 Volt = 32,61 Ampere/0, 5 (efficiency) = 65,22 Ampere
A digital amplifier with identical performance would be calculated as
follows:
450 Watt/13,8 Volt = 32,61 Ampere/0,75 (efficiency) = 43,48 Ampere
You can now gather the right cross-section from the table below.
Supposing that a 20 qmm power cable has a resistance of 8 Ohm
within the length of one meter. If we sum up the resistances of a 5 m
plus-cable and a 2 m minus-cable we get 5,6 m Ohm.
This means for an analogue amplifier:
65,22 Ampere x 0,0056 Ohm = 0,37 Volt
The voltage is only 13,43 Volt. A new calculation would be the
following:
13,43 Volt x 65,22 Ampere x 0,5 (efficiency) = 438 Watt.
This would in theory mean a loss in power of 12 Watt.The conductivity
becomes worse if the temperature is rising. The most important factors
in this case are the ambient temperature and the current intensity.
Transient resistances occurring at terminals and fuses also influence
the result negatively.
Now consider the calculation of the digital amplifier.
Cable cross-sections and length are the same.
43,48 Ampere x 0,0056 Ohm = 0,24 Volt
Remaining voltage: 13,56 Volt
13,56 Volt x 43,48 Ampere x 0,75 (efficiency) = 442,2 Watt
Loss in power: only 7,8 Watt.
190
The amplifier’s switching power supply tries to compensate this loss in
power. The success is dependant on the quality of the amplifier. But it
will be surely the battery that will suffer and a usual battery can deliver
high power only up to a certain point.
The amplifier sooner or later is pushed to its limits which means
distortions and a worse sound. Sometimes even the loudspeakers
may be destroyed. In this case an amplifier may supply the
loudspeaker outputs with direct current.
This example makes clear that digital amplifiers are not only smaller,
need less power and require in most cases a smaller cable cross
section, they also do not stress the battery that strong which will
therefore live longer. If the amplifiers have similar Watt indications
the sound of the digital amplifier will be much cleaner in the threshold.
Developing the cable belonging to the „Professional Line“ we intended
after all to optimise the internal resistance of a cable. By a special
treatment of the stranded wire’s surface the internal resistance was
decisively reduced. If we connected for example a 20 sqmm
Professional Line cable with a resistance of 0,6 m Ohm/m to an
analogue amplifier, the following results would be achieved.
65.22 Ampere x 0,0042 Ohm = 0,27 Volt
value of voltage 13,53 Volt
13,53 Volt x 65,22 Ampere x 0,5 (efficiency) = 441,2 Watt
Using a Professional Line cable the result would show a plus of
3,2 Watt. This plus would be achieved without manipulating the
output stage. Using high quality cables, this result can be transferred
to all kinds of amplifiers.
If the output stage has a low ohm charge and/or is working bridged,
the increase of Watt-output has to be adapted to the cross-section
of the cable.
The right choice of the power cable
151-200 A 20 35 50 70 95 95 120 120
101-150 A 20 35 35 50 70 70 95 95
81-100 A 10 20 35 35 50 50 50 70
61- 80 A 6 20 20 20 35 35 50 50
41- 60 A 6 10 20 20 35 35 35 35
31-40 A 4 6 10 20 20 20 20 35
21-30 A 4 6 10 10 20 20 20 20
0-20 A 4 4 6 6 10 10 10 20
2 m 3 m 4 m 5 m 6 m 7 m 8 m 9 m
The calculation of the cable cross sections was made on the basis that the
maximal voltage drop over the length of the cable should not exceed 0,5
Volt. The length indications are valid for the one-way length from the battery
to the amplifier. The indicated cross sections refer to the go-and-return
line (plus- and compound-impregnated conductor).