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Output Current Limiting
In terms of maximum available output current, there
are basically three amplifier type options:
o An amplifier with a reasonable limit placed on
the maximum available output current
o An amplifier with no limit placed on the
maximum available output current, which will
either blow a fuse or self destruct if excessive
current is drawn, for example through a dead
short
o An amplifier with a very high limit placed on
the maximum available output current, but
designed not to blow a fuse if this very high
current is drawn
If the maximum current drawn from an amplifier
with maximum available current limiting is reached
under very loud music conditions (the first and third
Loudspeaker load
Output power
impedance
8 Ohms
150 W
4 Ohms
300 W
2 Ohms
600 W
1 Ohm
1200 W
Table 3
amplifier types above), highly obvious "cracking"
overload sounds may be heard. Note that this
overload sound may also occur if a loudspeaker
overloads or if any amplifier suffers voltage
overload.
There is an expectation in the audiophile electronic
industry that a high-end amplifier should be capable
of delivering exactly double the output current for a
halving of the loudspeaker impedance (down to 1
ohm) at the maximum output voltage that the
amplifier can produce.
This requires an amplifier of the second and third
type above. The table below lists an example of an
amplifier rated at 150 watts output into 8 ohms.
r.m.s. output
Peak output voltage
current
49 V
4.33 A
49 V
8.66 A
49 V
17.32 A
49 V
34.64 A
20
Peak output current
6.12 A
12.25 A
24.5 A
49.0 A
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