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Class A into Class AB

What is the goal of a designer who makes intergrated amps that have class A for x amount of watts before it goes into class AB? Are there any examples of this being implemented well? I get this feeling that it’s kind of just a marketing thing...where people think they are getting some quality class A without the very high price tag. I was particularly looking at the CODA CSiB amps where you have three choices of how much of your first watts are class A. I have since found a few other respectable brands that implement this as well. I have yet to come across anyone who has heard much of difference between AB amps and one’s that’s state "first X amount of watts..." Class A/AB. Anyone have any experience with these kind of integrated amplifiers? Just looking for a little bit of understanding as I’m trying to upgrade my amplifier.
tmac1700

Showing 5 responses by holmz

holmz's avatar
holmz
2,328 posts
 
It is mostly marketing jumbo jumbo.
Any biased AB designed will be biased, and the amount is either 0.6V or more than 0,6V (like 1.2V).
So a 1.2V bias design always runs as class A under 1.2v.
So yeah it it marketing.

If it was a Class-A on the tweeters, and an AB on the MR and a class B on the woofers, then that is a different beast of a thing.
holmz's avatar
holmz
2,328 posts
 
It is mostly marketing jumbo jumbo.
Any biased AB designed will be biased, and the amount is either 0.6V or more than 0,6V (like 1.2V).
So a 1.2V bias design always runs as class A under 1.2v.
So yeah it it marketing.

If it was a Class-A on the tweeters, and an AB on the MR and a class B on the woofers, then that is a different beast of a thing.
holmz's avatar
holmz
2,328 posts
 
I do practically all of my listening in Class A - if you believe those seductive dancing meters :-)
I believe you and the others, including myself, that in an RMS sense… it is mostly Class-A.

Just the crest factor of a lot of music can be ~13dB. So that often jumps the peaks up to Class-AB.
Maybe at 60-65dB it is under/within Class-A.
But at 75-80dB those peaks will be above the meager level where the bias disappears it being qualified as “Class-A like” operation...”
And it has historically been in the louder sections of music where I have heard the grainy’ness, so maybe that was cross over distortion from Class-AB?
holmz's avatar
holmz
2,328 posts
 
The meters on home audio gear are almost never calibrated and more often than not mislead rather than inform


How coils they be accurate when they often report < 1W ?
holmz's avatar
holmz
2,328 posts
 
When I first put a voltmeter on speaker terminals I was “shocked” at how low the voltage was… and that was with 8 ohm speakers.

By the time you get to 4-5v it is almost shaking the house.
A meter is a pretty easy thing to make, and they have been doing those for around century.
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