I've tried it with 3 different IC to the preamp and with 2 different speakers, same result. The heat/warm comes mostly from the sides, not really from the top. If the rule is to be able to keep your hands on it for more than 1 minute, so that should be normal and I can leave with that (the sound is fantastic). Surpised to see that this fact doesn't seem to borther other owners... Maybe, I am not difficult...