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In Reply to: RE: Is there any real benifit sonically between class A, AB etc... posted by Disbeliever on June 27, 2016 at 22:56:49
Well designed Class AB amps, particularly the high power ones, are class A at about 10% to 15% power output and that is where most of music is anyway, even if you play it real loud most of the music will not need much power and you are well within Class A sound.
Vahe
Follow Ups:
That's a misunderstanding of how things work.It is true that in a Class A/B amp both devices are conducting the full 360 degrees at low power but there is more to the operation of Class A than that.
In a Class A design the devices are biased to idle right in the middle of the "sweet spot" (where the device gets real linear) they are then only operated in the sweet spot unless over driven.
With Class A/B each device is biased well below the sweet spot and each device (in turn) only reaches the sweet spot after the other device has turned off.
A Class A/B amplifier operates in Class A/B and a Class A amplifier operates in Class A.
The only thing that is the same between a Class A/B amp running at low power and a Class A amp is the fact that neither device is being cutoff but, as I said, there's more to Class A operation than whether or not the devices are being cutoff.
Many will argue with me about what is and what isn't Class A but a Class A/B amp running low power will not have the low distortion or sweet sound of a Class A amplifier because the devices are not running in the "most linear portion of the dynamic curve" and in a Class A amp the devices will be.
Just because the devices are not being cutoff doesn't mean they are running in the "most linear portion of the dynamic curve" and good practice is to run the devices in a Class A design in the "most linear portion of the dynamic curve".
So I guess a person could say that a Class A/B amp running at low power is running Class A but I don't think anyone could argue that they are running "good practice" Class A.
All the examples in the books that show Class A show the devices running in the "most linear portion of the dynamic curve".
A Class A/B amp DOES NOT DO THAT, ever.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 06/29/16 06/29/16 06/30/16
Very nice explanation and I am sure is a surprise to many here who believe manufacturers hype about "high bias" Class AB or running Class A for the first Xwatts.
Never get anywhere near the non-linear saturation region and never get anywhere near the non-linear cutoff region.
That's the true meaning of Class A and the examples of Class A given in all the books.
In the sweet spot and only in the sweet spot!
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
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