In this second part, Stochino presents and discusses the results of his recent investigations and experiments on the last two classes of error-distortion correction systems introduced in part 1, feed-forward error correction and mixed feedback and feed-forward error correction schemes. Addressed in more detail is true feed-forward error correction where a small ferrite-core wideband transformer, incorporating main signal flux cancellation, is used in the output summer of a feed-forward 100W audio power amplifier. These more recent developments achieve a total harmonic distortion lower than 0.0005% and an intermodulation distortion less than 0.0001% at all audio frequencies and power levels up to 120W into 8Ω. Giovanni also takes a closer look at a new hybrid arrangement employing both BEF and FFEC in order to both mitigate some inherent problems of the ferrite-core wideband transformer, and potentially achieve in audio power amplifiers harmonic and intermodulation distortion levels lower than 1ppm (0.0001%) at all audio frequencies and power levels.
