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Original Message

Class B does not have to have a zero crossing artifact.

Posted by Ralph on February 11, 2025 at 09:34:25:
This will ALWAYS cause a zero crossing distortion because of the non-linearity in transistors turn on and shut off. This cannot be eliminated through the use of negative feedback and no matter how small it will always produce unpleasant distortion.

This statement is false. I have an example on a shelf here at the shop- the Electro Voice A-20C. Its class B and exhibits no crossover artifact at all- just as the Topping amp of this thread. I refurbished this EV amp because I was curious about this issue. It has no measurable or audible zero crossing artifact at any power level.

A lot of class B tube amps did have a zero crossing artifact. When the magnetic field in the output transformer collapsed when the power tubes were in cutoff, a spike was generated. The EV gets around that by using a Circlotron output circuit.

Solid state class B amps simply have to have the bias close enough that the crossing is seamless. They don't have the spike problem because no output transformer. They don't have to have an A region bias to pull this off- just good design.