Page 70
Bittner Audio - Application Handbook
4.3.
Useful Things
Load-to-Power relation in 100V systems
10 Ohm = 1000 W
20 Ohm =
500 W
25 Ohm = 400 W
40 Ohm =
250 W
50 Ohm =
200 W
100 Ohm = 100 W
Crest Factor
The Crest Factor of an amp represents the relation between the peak voltage and the RMS value.
It can be taken as a measurement of the quality of the response of an amp.
Crest Factor =
Peak
RMS =
1
√
2 x Peak
Resistance - Capacitance - Inductance
Ohm’s Law:
U = I x R
I =
U
R
R =
U
I
Power:
W = I² x R
W =
U²
R
W = U x I
Resistors in series:
R
ges
= R
1
+ R
2
+ …. + R
n
Resistors parallel:
R
ges
=
1
1
R
1
+
1
R
2
+…+
1
R
n
Voltages in dBu and dBV
10
V =
20 dBV =
22 dBu
1,55
V =
4 dBV =
6 dBu
1
V =
0 dBV =
2,2 dBu
775 mV =
-2,2 dBV =
0 dBu
316 mV =
-10 dBV =
-7,8 dBu
"dB"-Relations
Voltage:
dB = 20 log
10
E
1
E
2
Power:
dB = 10 log
10
P
1
P
2
Conversion of THD to "dB below signal level"
THD %
dB
below
signal
THD %
dB
below
signal
THD %
dB
below
signal
100
0
0,5
-46
0,01
-80
10
-20
0,25
-52
0,005
-86
5
-26
0,1
-60
0,0025
-92
1
-40
0,05
-66
0,001
-100
Voltage to Power
Volts
Watt
4 Ohm
Watt
8 Ohm
Volts
Watt
4 Ohm
Watt
8 Ohm
63,2
1000
500
20
100
50
44,8
500
250
14,1
50
25
31,6
250
125
10
25
12,5
28,2
200
100
6,3
10
5
22,4
125
62,5
2
1
0,5
