This is a MOSFET power amplifier designed by the makers to be state of the art; I'm sure it was made to showcase their own Hitachi semiconductor devices as MOSFETs were taking their time to be accepted when this was made. It has amazing specifications and it does sound really. really good. Dual mains transformers and power supply as well as separate output circuit boards make this a truly dual mono design. Huge blue light meters make it a real looker. It runs warm (hot even it's mostly biased into class A) and seems to have no problem driving any speakers; I have heard some comments regarding shutting down with low impedance speakers but I have used 4 ohm speakers with no problems. BUT if you bridge it or use two sets of speakers it clearly says 8 ohm (nominal) minimum on the back! Also have it serviced if there is a hint of any problems; at the age of these (Introduced in 1984) there may well be dry joints (as shown below) that only give trouble when the amp is warm and this amp runs very warm when correctly calibrated; a good winter amplifier.
Just a note: with all this apparent power it should "sound louder" than other lower power amplifiers but remember this is running in class A much of the time so efficiency is much lower; some speaker driving power is sacrificed to get the best performance (low distortion) and that is why it sounds so good.