I'd like to propose a new class of operation for tube amplifiers. " Linear Class A"

In a Linear Class A amplifier none of the tubes are allowed to operate outside the linear portion of the operating curve for the tube.

Of course, this form of operation is not new. All single ended circuits have to be linear class A. If not, the distortion would be so high no one would want to listen to them. But in a push-pull amp. the circuits can be non-linear.

In a Class AB push-pull amp. the non-linear output of one half of the push pull is combined with the non-linear output from the other half to create a waveform that looks linear.

In a non-linear push-pull Class A amp. (an amp. where the current flows at all times but not in a linear way) the same combining happens.

I propose that a Linear Class A push-pull amp. will have better sound and less distortion than a non-Linear Class A push-pull amp.

The need for this new classification arises from my belief that people are being mislead by ads for push-pull amplifiers that claim "Pure Class A" with no regard for symmetry.

It's true that as long as current is flowing at all times the amp. is considered Class A or even Pure Class A, but most people think of single ended amps. that are Linear Class A when they read the words "Pure Class A."

Thanks for taking time to read this. Please let me know your position on my proposal. Tre' _____________________________________________________________________________

I wrote the above after letting myself be convinced by a few, that the over simplistic definition of Class A was fact. (As long as plate current never cutsoff completely, then it's class a.) I then did some more research and I am back to my original position that Class A is when the tube is biased to operate only in the most linear part of the curve. The Radio Handbook 14th Edition page 98 "......Such an amplifier is normally operated in the center of the grid-voltage plate-current transfer characteristic and gives an output wave-shape which is a substantial replica of the input wave-shape."

The Radio Handbook 38th Edition page 65 A Class A amplifier-- "...is one operated so that the wave shape of the output voltage is the same as that of the signal voltage applied to the grid." Tremaine Audio-Cyclopedia 2nd Edition page 523 "The quiescent plate current is selected for a value in the most linear portion of the plate-current characteristic."

Page 543 "What is a class A amplifier? An amplifier in which the grid-bias voltage is set to approximately one-half the cutoff voltage to obtain linear operation."

Page 604 "When operating as a single tube, class a, little distortion exists because the grid signal operates in the most linear portion of the dynamic characteristic." Taking a look at the graph found on page 543, it is clear that Tremaine thinks that Class A does equate to linear operation. At least as linear as can be obtained from the chosen tube.

I included figure 1 to show why, in figure 3, all of what appears to be linear is not. Notice that the horizontal lines on figure 3 correspond well with where the tube leaves the truly flat part of the curve, as shown on figure 1.

So, there is no need for a new class of operation. Class A is when the tube (all the tubes) in an amplifier operate only in the linear part of the curve always staying away from the non-linear area close to cut-off and saturation.