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DLS SOUND HANDBOOK - FORMULAS AND FACTS
DECIBEL - dB
dB is a unit used to describe a realation. It´s used to
describe an amplification as well as an attentuation.
At an attentuation a minus sign is put before the figure.
An amplification is the relation between the input and
the output signal. In can be valid for voltage, current
or power.
When used for power amplification you must
remember that current x voltage = power. This means
that the relation becomes larger, see the table below.
Examples of fixed dB relations:
For voltage and current:
dB
Amplification
0 dB
1 time
1 dB
1,1 times
3 db
1,4 times
6 dB
2 times (double)
10 dB
3,16 times
20 dB
10 times
The amplification increases logarithmic.
For power:
dB
Amplification
0 dB
1 time
3 dB
2 times
6 dB
4 times
10 dB
10 times
20 dB
100 times
An attentuation of -6 dB is a half for voltage and
current and a quarter when talking about power.
CONNECTION OF CAPACITORS
Capacitors acts in the opposite way as resistors when
connected in series or parallel.
IN PARALLEL:
The total capacitance when connecting capacitors in
parallel is the sum of each capacitor.
C tot = C1 + C2 + C3 + C4 etc.
10 μF
50 μF
C tot = 10 + 50 + 50 + 100 = 210 μF
1 μF = 0,000001 Farad (10
1 nF = 0,000000001 Farad (10
1 pF = 0,000000000001 Farad (10
50 μF 100 μF
-6
)
-9
)
-12
)
CONNECTING RESISTORS
The formualas below is valid when connecting
resistors and inductances in series or in parallel.
It can also be used for speakers.
IN SERIES:
The total resistance is equal to the sum of all
resistors in the connection.
R tot = R1 + R2 + R3 + R4 etc.
4 Ω
8 Ω
R tot = 4 + 6 + 8 + 12 = 30 Ω
IN PARALLEL:
When connecting in parallel the total resistance
always becomes lower, it is always lower than the
lowest resistor value in the connection.
Formula:1 = 1 + 1 + 1 + 1
R
R1
4 Ω
4 Ω
1 = 1 + 1 + 1 + 1
R
4
When connecting only two resistors in parallel you
can use the formula below.
R1 x R2
Ex.
R =
R1 + R2
IN SERIES:
When connecting capacitors in series you calculate
in the same way as for resistors connected in parallel.
Formula: 1 = 1 + 1 + 1 + 1
C
C1
50 μF
10 μF
50 μF
100 μF
1 = 1 + 1 + 1 + 1
C
10
50
When connecting only two capacitors you can use
the same formula as in the example with two
resistors connected in parallel above.
3
6 Ω
12 Ω
R2
R3
R4
8 Ω
8 Ω
R = 1,33 Ω
4
8
8
4 x 8
32
= 2,66Ω
=
4 + 8
12
C2
C3
C4
C= 6,66 μF
50
100
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