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AUDIO FORUMS >> General Discussion and Support >> Merits of Class A2?
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Message started by Brian on 08/04/18 at 19:51:29

Title: Merits of Class A2?
Post by Brian on 08/04/18 at 19:51:29

Operating class A is Single Ended operation. Class 2 is when grid current flows for some part of the cycle, i.e. the grid is driven slightly positive on signal peaks.
Class 2 requires a DC-coupled driver stage, or a very low impedance transformer-couple. The advantage of class 2 is the complete lack of transient intermodulation, commonly known as "blocking distortion".

I have read that some listeners prefer Class 2 saying it is more dynamic.

I wonder if Decware might have interest in making a Class A2 amp.
And I wonder if it might be an especially good choice as a Bass amp in a sub woofer system.

Brian

Title: Re: Merits of Class A2?
Post by 4krow on 08/04/18 at 21:30:44

Brian,

I appreciate that you have brought up this topic. I have only vaguely heard of this class A2 concept, and it has been a long time ago. So, the grid bias is set to compensate for peaks? I thought that all a circuit was really capable of is class A in the more traditional sense. I am interested to know more about these two ways of biasing, if that is what is happening, and does it produce a greater load on the tube itself, etc.

Title: Re: Merits of Class A2?
Post by Brian on 08/07/18 at 03:09:30

4krow said:
"I appreciate that you have brought up this topic."

I hope this thread will generate some interest in what a few listeners have reported as being a great thing, but which I have no experience with and next to no understanding of.

"So, the grid bias is set to compensate for peaks?"

I did not interpret it that way. My best understanding is that power increases on dynamic peaks, the higher the peak, the greater the power increase until the limit of available power is reached. So class 2 operation is a dynamic range expander. It makes the music seem more real and more lively.