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Arny Krueger
 
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"Tim Martin" wrote in message

"Don Pearce" wrote in message
...

As far as I am aware, there are no class B amps around
these days. Anybody know of any?


Presumably this "high end audio manufacturer" makes Class
B amplifiers:

http://www.norh.com/docs/amps/



"... 99% of all audio amplifiers today are Class B.


Absolutely totally and completely false.

Here is a true statement:

99.99% of all audio amplifiers today are Class AB

Class B amplifier can be built today so that its
distortions
are well below what the human ear can detect and nearly
to the point where it is unmeasurable.


Nope, a true class B amplifier is rare thing because it
depends on precise biasing that cannot be controlled well
enough.

Many amplifiers call themselves Class A/B.


Yes, and there's nothing wrong with that.

In reality, very few are.


The author is living in an alternative universe.

Early Class B amplifiers had a problem
known as switching delay.


Some did.


In a class B design, a
transistor works 50% of the cycle while another
transistor works 50% of the cycle. In early class B
amplifiers, there was a distortion created between the
time the devices were switching back and forth. Some
people referred to this distortion as notch distortion
because there was a notch appearance on an oscilloscope
between the two waveforms.


This would be true except that almost zero SS amps have been
built this way.

Class A/B was created to leave the transistor conducting
while the second transistor was conducting. This created
an overlap between the two signals.


So far so good.

The problem with this
approach is that it created its own distortion called
gumming.


I've heard of a lot of weird stuff, but I've never heard of
gumming distortion.

This means that the signal would get a little
fatter where the two devices were both conduction.


Spare me!



Today, if you look at a properly designed Class B
amplifier on a scope, you will see no switching
distortion."


Probably, you will because true class B is a single, very
exact point and its hard to hold.