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Old 16th December 2004, 07:50 AM   #1
freedom is offline freedom  Denmark
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Default Classes of operation vs. sound quality

Hi All

I´m under the impression that "non-hifi-nerds" eg. everyday peoble generally believe that Class A sounds better than B, B better than C, C better than D and so forth.

Everyone (in here) knows that the indexes only refers to the collector current angle, for class A, B and C, and that Class D is PWM. We also know that class AB can be made to sound as good, and maybe even better than class A... know this is an issue to be discussed beyond the end of time.

But: Am i right when saying that not-so-well-informed users of common hifi-equipment generally believes that the index of classes is reverse proportional to sound quality?


Thanks in advance
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Old 16th December 2004, 08:43 AM   #2
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Not - so - well - informed - users are here also, so you will get many oportunity informations . Class of amp tell anything about real quality. I have heard many " A ", which was s...s and several " AB " which was excellent .
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Old 16th December 2004, 09:35 AM   #3
MikeB is offline MikeB  Germany
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I think, a well designed ClassA should always outperform any ClassAB,
but a well designed ClassAB will always outperform a "standard" ClassA.
It's just that ClassA can't have crossoverdistortion and should always
be more linear, especially for higher freqs.
The quality of an amp mainly comes from how good the design is,
not topology or class.

For example, my own ClassAB outperforms my MF-A1, a commercial ClassA.
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Old 16th December 2004, 09:59 AM   #4
NUTTTR is offline NUTTTR  Australia
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I've heard good Class a/b's and good class A's, but the day you show me a good sounding class b...!!! A class b i had sounded like ****!!! It was horrible...
But i don't know about class a/b vs a, as any very well designed amp will sound good, a very good class a vs very good class a/b the difference should be so minimal you shouldn't be able to tell....
However "technically" i'd say the class a would be 'better' in this case... however i cannot tell you why or how, but cool factor alone
Aaron
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Old 16th December 2004, 10:19 AM   #5
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With boxes with average efficiency ( cca 90 dB/w or less ) you need minimally 100 W/ ch for preservation of natural sound dynamic. On this look is funny amp with output power 10 W. With typical efficiency of class A ( cca 25 % ) you get by amp 2*100 W of output power 600 W of continuous heat. I don't like " good sounding " stove .
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Old 16th December 2004, 01:56 PM   #6
Mr Evil is offline Mr Evil  United Kingdom
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In an ideal world with ideal transistors, all amplifier classes give identical outputs. In practice, all can give similarly good performance (except class C, since it isn't possible to build a pure class C audio amp), but class A starts off with the advantage of lacking crossover distortion.

Class A amps are not so common because of the ridiculously low efficiency which overrides any possible distortion advantage.

I have a feeling that technology advances, class D will give the best performance, since it is theoretically capable of both extremely low distortion and near 100% efficiency at the same time.



Quote:
Originally posted by NUTTTR
...but the day you show me a good sounding class b...!!!
I've heard plenty of good sounding class B amps. In fact a properly biased class B has lower distortion than class AB, it's just more difficult to get right.
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Old 16th December 2004, 02:50 PM   #7
jam is offline jam  United States
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A simple test would be to take a class A amp and reduce the bias to class AB and compare the differences.

Most people would choose the amp in class A. There are differences in the sound that occur that cannot be attributed to distortion alone.
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Old 16th December 2004, 03:20 PM   #8
djQUAN is offline djQUAN  Philippines
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Quote:
Class A sounds better than B, B better than C, C better than D and so forth.
class B is definitely better than class C. but class D is so much better for audio than class C.
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Old 16th December 2004, 03:25 PM   #9
moamps is offline moamps  Croatia
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Quote:
Originally posted by Mr Evil
...... a properly biased class B .......
What does it exactly mean?

Regards,
Milan
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Old 16th December 2004, 03:30 PM   #10
MikeB is offline MikeB  Germany
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Quote:
Originally posted by jam
A simple test would be to take a class A amp and reduce the bias to class AB and compare the differences.

Most people would choose the amp in class A. There are differences in the sound that occur that cannot be attributed to distortion alone.
Typically, ClassA use a different topology that is not able to properly
work in ClassAB. Escpecially the singleended versions can't work ClassAB.

"Biasing in ClassB" ???

I thought ClassB has a biasing of 0ma ?

Mike
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