Placebo? I don't think so. I got to thinking about this some time ago after I was blown away by the sound after sitting in on a jam where there was an Aguilar DB750. It inspired me to drag out my old AB power amps, notably a Crown XTi 4000 (I don't think I can even lift my Crest CA-9 anymore), and run various pres through them, and darned if I don't like the sound better. Why? It's deeper while being tight and articulate. Wattage is similar. Cabs are the same. I just read through a thread on TB about there being essentially no difference, tonally, between AB and D, but to me I think it sounds and feels different. I'm wondering about higher damping factor; my AB amps are >500, and to my non-electronically trained brain, that equates to better control over the speaker, hence tightness. So what am I hearing?