I've been running four of these in the driver stage of my ASL Hurricanes for thousands of hours now, and they still sound (and test) fantastic. Smooth and neutral would be the way I'd describe them. Their great looks are an added bonus. I've rolled countless 6SN7's (incl. the famed TSRP's and Syl. Bad Boys), and these can easily go head to head with them. Also, theses are probably more accurate to the source.