@charles1dad The Berning amplifier in question can run feedback or none; being SET its distortion signature is based on a quadratic nonlinearity (2nd harmonic). In order to have a cubic nonlinearity (based on 3rd harmonic) the amp has to be entirely differential from input to output.
The ear treats both the 2nd and 3rd the same way (contributes to 'warmth' and 'richness') but in general an amplifier with a predominate 3rd will have considerably less overall distortion (typically 1/10th) than one based on the 2nd, and as the distortion order is increased, the product falls off faster. This is especially beneficial because the ear is so sensitive to the higher ordered harmonics.
The advantage of the Berning amplifier over a traditional SET is that the output transformer is not nearly as bandwidth limited and it does not have the saturation issues. So it can be made considerably higher power as well!
The ear treats both the 2nd and 3rd the same way (contributes to 'warmth' and 'richness') but in general an amplifier with a predominate 3rd will have considerably less overall distortion (typically 1/10th) than one based on the 2nd, and as the distortion order is increased, the product falls off faster. This is especially beneficial because the ear is so sensitive to the higher ordered harmonics.
The advantage of the Berning amplifier over a traditional SET is that the output transformer is not nearly as bandwidth limited and it does not have the saturation issues. So it can be made considerably higher power as well!