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Hi Bill,
Isn't the RMS Power rating of an audio amp much lower than its=20
peak output capability? When I was in high school drooling over
high-end stereo amps, I recall magazines like Stereo Review would
rate audio amplifiers in terms of their peak output capability=20
as well as RMS output.=20
Yes, until the Federal Trade Commission (FTC) became involved after =
numerous consumer complaints were filed over deceptive advertising =
practices relating to audio power amplifier specifications. In the late =
'70s, the FTC stepped in and required that all audio power amplifier =
manufacturers must advertise their published power specifications in =
terms of "continuous power." Many of the better manufacturers complied, =
others did not. Other terms like peak power, intermittent peak power =
and many others were crafted by shrewd marketing departments. It's =
interesting to look at the amplifier power specs in an old Lafayette or =
Allied Radio catalog from the early '70s. Not surprisingly, we continue =
to have this problem today in the advertised specifications of =
commercially-made amateur radio power amplifiers. Stating power in =
terms of "Continuous Power, Unlimited Duration" takes into account the =
power envelope over time, since the power can fractionally change over a =
snap-shot in time. Anything less than continuous, no-time-limit implies =
that the amplifier may be *capable* of achieving the rated power =
specification with a continuous power envelope but only over short =
durations OR over continuous a duration, but not a continuous envelope. =
=20
The term "RMS POWER" is in and of itself an oxymoron. Applying RMS =
strictly to the power component yields a value of zero. Since power can =
never be negative, I suspect that the original intent was to apply RMS =
to either the voltage OR the current value in determining "RMS Power," =
not the power value itself. I believe Mike correctly stated this in the =
power calculation from his previous post.
-Paul, W9AC
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<DIV><FONT face=3D"Courier New" size=3D2>Hi Bill,</FONT></DIV>
<BLOCKQUOTE dir=3Dltr=20
style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3D"Courier New" size=3D2>Isn</FONT><FONT =
face=3D"Courier New"=20
size=3D2>'t the RMS Power rating of an audio amp much lower than its=20
</FONT></DIV>
<DIV><FONT face=3D"Courier New" size=3D2>peak output capability? When =
I was in=20
high school drooling over</FONT></DIV>
<DIV><FONT face=3D"Courier New" size=3D2>high-end stereo amps, I =
recall magazines=20
like Stereo Review would</FONT></DIV>
<DIV><FONT face=3D"Courier New" size=3D2>rate audio amplifiers in =
terms of their=20
peak output </FONT><FONT face=3D"Courier New" size=3D2>capability =
</FONT></DIV>
<DIV><FONT face=3D"Courier New" size=3D2>as well as RMS output. =
</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>Yes, until the Federal Trade =
Commission (FTC)=20
became involved after numerous consumer complaints were filed over =
deceptive=20
advertising practices relating to audio power amplifier=20
specifications. In the late '70s, the FTC stepped in and =
required=20
that all audio power amplifier manufacturers must advertise their =
published=20
power specifications in terms of "continuous power." Many of the =
better=20
manufacturers complied, others did not. Other terms like peak =
power,=20
intermittent peak power and many others were =
crafted by shrewd=20
marketing departments. It's interesting to look at the amplifier =
power=20
specs in an old Lafayette or Allied Radio catalog from the early =
'70s. =20
Not surprisingly, we continue to have this problem today in the =
advertised=20
specifications of commercially-made amateur radio power =
amplifiers. =20
Stating power in terms of "Continuous Power, Unlimited =
Duration" takes=20
into account the power envelope over time, since the power can =
fractionally=20
change over a snap-shot in time. Anything less than continuous,=20
no-time-limit implies that the amplifier may be *capable* of achieving =
the=20
rated power specification with a continuous power envelope but only =
over short=20
durations OR over continuous a duration, but not a continuous =
envelope. =20
</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>The term "RMS POWER" is in and of =
itself an=20
oxymoron. Applying RMS strictly to the power component =
yields=20
a value of zero. Since power can never be negative, I =
suspect that=20
the original intent was to apply RMS to either the voltage OR the =
current=20
value in determining "RMS Power," not the power value itself. I =
believe=20
Mike correctly stated this in the power calculation from his =
previous=20
post.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>-Paul, W9AC</FONT></DIV>
<DIV><FONT face=3DArial =
size=3D2></FONT> </DIV></BLOCKQUOTE></BODY></HTML>
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