In the early days of class d I bought a 450w amp to biamp my speakers with a tube top end and a cube dsp to contour for my room nodes and to integrate with my 120w tube amp. As it happened, the addition of 450w of class d power degraded the sound and couldn’t compete with the impact or sound quality of 120 tube watts shared output and the class d went to the beach house to do duty there. Since that time I have heard numerous class d amps of varying cost and quality but found characteristics that repeated, particularly in the upper midrange and high frequencies which seemed exaggerated or “hard” whereas the lower mid and bass seemed to lack force or decay. This experience is years old and I have not heard the newest crop of gallium transistor based amps, except through YouTube videos. I wonder what the design issues are with these amps. The high amount of feedback used to make them work seems to sterilize the sound of those high feedback class a amps I have heard and therefore may do the same in class d. The promise of a cool running amp that delivers great sound is still enticing but I have not yet heard anything that I would replace my tube amps with. What is your experience and for designers, what keeps class d from competing with good class a?