On Tue, 26 Feb 2008 13:16:26 -0800, Arny Krueger wrote
(in article <S8ydnYg7ytu6H1nanZ2dnUVZ_qelnZ2d@[EMAIL PROTECTED]
>):
>
> "jamesgangnc" <james@[EMAIL PROTECTED]
> wrote in message
> news:13s6so0o3qqg69@[EMAIL PROTECTED]
>
>>> Surprisingly, these surround receivers actually do put out 100 watts
RMS
>>> each for all 5 channels concurrently, or 85 watts RMS each for 7
>>> channels concurre
>
>> If one of those cheap surround sound recievers is putting out 500 watts
>> rms then I'm betting it's a class d amp.
>
> Generally, no.
>
> At the 100 wpc level it is still generally cheaper to make a class AB
> amplfier than a Class D.
>
>> And that's why the distortion figures suck.
>
> Just because an amplifier is Class D (switchmode) does not mean that it
> necessarily has high distortion.
>
>> A good class ab amp will list continuous rms watts for 8 ohms and 4
ohms
>> with .1 thd or lower.
>
> That is about specsman****p, not usable performance. Yes, a lot of
receivers
> are giving power specs at 0.7% THD and the like. But, if they would back
> their power ratings off by say, 10%, then the THD would probably be
below
> 0.1%. There is hardly any audible difference between a clean 100 watts
and a
> clean 90 watts. For some reason they want to specify that the amp has
100
> wpc, and they are forced to specify more distortion than most are
> comfortable with to do it. However, nobody runs an amp flat out all the
> time, and in normal listening, the 0.7% THD figure is pretty much
arbitrary.
There's also no audible difference between 0.7% THD and 0.1% THD. The ear
is
amazingly insensitive to the AMOUNT of THD especially below about 2%, but
it
can be somewhat sensitive to the KIND of harmonic distortion (even or odd)
and where that distortion occurs.
--
Do you know the difference between students like you, amateurs and
professional jazz musicians? Student bands and amateurs "almost" swing!
Fred Berry
Professor of Music
Stanford University
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