Miscellaneous data
Resistance of copper conductors (approximate)
SWG no. |
Diameter (mm) |
Cross-sectional area (mm2) |
Resistance/m (Ω) |
10 |
3.25 |
8.3 |
0.002 |
12 |
2.64 |
5.48 |
0.003 |
14 |
2.03 |
3.24 |
0.005 |
16 |
1.62 |
2.08 |
0.008 |
18 |
1.22 |
1.17 |
0.015 |
20 |
0.91 |
0.66 |
0.026 |
22 |
0.71 |
0.40 |
0.043 |
24 |
0.56 |
0.25 |
0.070 |
26 |
0.46 |
0.16 |
0.10 |
28 |
0.38 |
0.11 |
0.15 |
30 |
0.32 |
0.0B |
0.22 |
Standard prefixes for multiples and submultiples
Multiplication |
|
Prefix |
Symbol |
1 000 000 000 |
= 109 |
giga |
G |
1 000 000 |
= 106 |
mega |
M |
1000 |
= 103 |
kilo |
k |
1/1000 |
= 10–1 |
milli |
m |
1/1 000 000 |
= 10–6 |
micro |
μ |
1/1000 000 000 |
= 10–9 |
nano |
n |
Decibel equivalents for power and voltage ratios
Decibels |
Power ratio |
Voltage ratio |
0 |
1 |
1 |
1 |
1.26 |
1.12 |
2 |
1.58 |
1.26 |
3 |
2.0 |
1.41 |
4 |
2.51 |
1.58 |
5 |
3.16 |
1.78 |
6 |
3.98 |
2.0 |
7 |
5.01 |
2.24 |
8 |
6.31 |
2.51 |
9 |
7.94 |
2.82 |
10 |
10.0 |
3.16 |
20 |
100.0 |
10.0 |
30 |
1000 |
31.6 |
40 |
10 000 |
100 |
50 |
100 000 |
316 |
60 |
1 000 000 |
1000 |
Conversion factors
1 inch |
= |
2.54 cm |
|
1 foot |
= |
30.48 cm |
|
1 yard |
= |
91.4 cm |
|
1 mile |
= |
1609 metres |
(m) |
1 cm |
= |
0.394 inch |
|
1 m |
= |
39.4 inches |
|
1 km |
= |
0.62 miles |
|
1 m/s |
= |
2.237 mph |
|
1 mph |
= |
0.447 m/s |
|
|
= |
1.609 km/h |
|
1 kgm |
= |
2.204 lb |
|
1 pascal (Pa) |
= |
1.450 × 10–4 |
lb/inch2 |
1 atmosphere |
= |
1.013 × 10–5 |
Pa |
1 millibar |
= |
102 Pa |
|
Connectors
It is probably good practice to assume initially that any audio connectors one comes across are not inevitably wired correctly! There can be some deviations from convention. Within one's own system, consistency of connection is clearly very important, otherwise out-of-phase conditions may occur, hum may intrude and there might even be a total loss of signal. The tables below and on the next pages give the generally accepted conventions for plug and socket wiring. These are given as pin numbers rather than as diagrams, as the latter can sometimes cause confusion: it is easy to forget, for example, that a diagram may represent the front of a plug where one solders the wires on at the back!
Balanced circuits
Connector type |
Signal+ |
Signal- |
Earth (screen) |
XLR style |
Pin 2* |
Pin 3* |
Pin 1 |
3-terminal jack (e.g. PO style or so-called ‘stereo’ jack, 6.3 mm or miniature, wired for a single balanced circuit) |
Tip |
Ring |
Sleeve |
3-pin DIN (as fitted to some microphones) |
Pin 1 |
Pin 3 |
Pin 2 |
*XLR pins 2 and 3 are reversed by some organizations and in some, mainly American, microphones. When connected to equipment using the other standard, this can cause a phase reversal in balanced circuits and a possible loss of signal in unbalanced ones.
Unbalanced circuits
Connector type |
Signal+ |
Earth (screen) and signal- |
XLR style |
Pin 2* |
Pins 3* and 1 |
Phono |
Pin |
Sleeve |
2-terminal (6.3 mm or miniature) |
Tip |
Sleeve |
3-terminal jack (6.3 mm or miniature) |
Tip |
Ring and sleeve |
3-terminal jack (6.3 mm or miniature) wired for stereo |
L: Tip |
Sleeve |
*See note on previous table.
DIN connectors
Note that there can be variations depending on the manufacturer of the equipment.
DIN 180° (5-pin) (Stereo: L = Left, R = Right) | ||||
Microphones |
L |
Pin 1 |
Pin 2 |
Pins 3 and 5 |
|
R |
Pin 4 |
|
may carry the polarizing voltage |
Tape recorder inputs |
L |
Pin 1 |
Pin 2 |
|
|
R |
Pin 4 |
|
|
Tape recorder outputs |
L |
Pin 1 |
Pin 2 |
|
(Low impedance) |
R |
Pin 4 |
|
|
(High impedance) |
L |
Pin 3 |
Pin 2 |
|
|
R |
Pin 5 |
|
|