Re: Class/type of amp ?


"William Sommerwerck" <grizzledgeezer@xxxxxxxxxxx> wrote in message
news:giasid$h5j$1@xxxxxxxxxxxxxxxxxxxxxx
As we are all fully aware, language and linguistic interpretation changes
and develops all the time. It is a fact of life that we all accept,
otherwise we would all still be saying "thee" and so on, and "gay" would
still mean carefree and happy. The same is true of electronics. Meanings
change. The world moves on. "Class G" seems to have been accepted pretty
generally by manufacturers as the designation for the type of output
stage
topology under discussion, just as "Class D" is now accepted as a fully
digital amplifier, where bias points don't come into it at all, unless
you
consider 'hugely on' and 'hugely off' to be valid examples of the term.

Arfa, please see my other post. Most class D amplifiers are analog, not
digital..

The web in general, would seem to disagree with you on that one, William ...

http://www.pcmag.com/encyclopedia_term/0,2542,t=Class+D+amplifier&i=55417,00.asp
http://www.pcmag.com/encyclopedia_term/0,2542,t=amplifier+classes&i=55350,00.asp
http://en.wikipedia.org/wiki/Electronic_amplifier
http://www.answers.com/topic/class-d-amplifier
http://www.maxim-ic.com/glossary/index.cfm/Ac/V/ID/1063/Tm/class-D

and many many more examples. The signal in a class D amplifier is only
analogue at it's input, and at the speaker terminals after the low pass
filter that removes the HF PWM component. Thus, the whole amplifier is
fundamentally digital in the way that it amplifies the signal applied to it.



Yes, you could say that this is "A class-AB amplifier with switched
rails",
but how much easier to just say that it's "Class G" ... ??

For that to work, you'd have to have some organization -- such as the IEEE
in the US -- setting standards as to exactly what class-G topology is.


Well, to make it totally 'official', I guess that's so, but again, if you
use the web to search for definitions for class G, you will find that pretty
much all manufacturers and describers, use the same definition virtually
word for word, which would suggest that an unwritten 'standard' for what it
is, already exists.



I used to own Krell amplifiers. They were billed as class A, but they were
class A "only" up to about 1/4 or 1/3 full output. Given the crest factor
of
acoustically recorded music, this means the amplifier will rarely stray
from
class A. But strictly speaking, the amplifier is AB, with (very) high
bias.

Most amplifiers are biased only a little beyond class AB. My Parasound A21
amps are unusual, in that they're still in class A up to about one ampere,
which is high for not-horribly expensive amplifier. They are correctly
billed as high-bias class AB.


But surely, that emphasises the point that there are no true 'standards'
applied to the existing letters ?

Arfa


.

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