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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
henry53's avatar
henry53
280 posts
 
I use a Vincent Audio pre power SA 31 MK / SP 331 MK, first 10 watts are Class A. Calculations imply that would be 99% plus of my listening time. 
larryro2
137 posts
 
Why are you not using Class D?
hz79hc's avatar
hz79hc
24 posts
 
I found the real sweet spot.  I bought a 1970s vintage Yamaha CA-800.  A very nice class AB 55 or 60w into 8ohms ...with a wonderful *twist* above & beyond its classic look.

It has an operating mode switch whose purpose is to keep the amp operating solely in Class A mode (rated at 10w in Class A, I think)
-or- to operate normally in AB behavior and the stated power rating.  

Now, be -very- jealous!!  ;-)
I am not aware how many Yammie models had that nor do I know over what time period such a control was available.  Whether other manufacturers of that or any other era have offered such a control--I don't know...
Warren
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.
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