Hi, I bought a used Hevos 400B, which is the older type, the one they had before they made the new 400D. The 400B has an analogue solid state power stage and a tube pre-amp. It weighs 11 kilos, and (!) has NO ventilator but aluminium cooling ribs, which is enough. So: it is silent. The sound: clear but with warmth and good low/mids. Not very coloured. At first you think: is this all? But when you switch back to your old amp, that old amp will sound muffled, or thin. And you will want to get back to that superior, detailed but always 'bass like' amp the the Hevos is! Love it!