Solid state stereo power amplifier. Spec I have from a Stereophile review, 85W into 8 ohms, 170W into 4 ohms. input impedance: 100k ohms. Its pure class A and no feedback. I bought this amp a few years ago from a tech, its the most highly beautifully polished aluminum chassis I have ever seen. There are a few scratches but they are hard to see. I first read about this amp in my Audio Critic bulletin as their reference amp, but they stopped printing that in 81' so never reviewed it. I seen an Stereophile review in my 1988 January issue on it by JGH. He had the older styled internally amp which it had five separate power supplies run the amp. 2 transformer for the two output stages, 2 transformers for the voltage amplifiers and one for accessories includes onboard microprocessor that checks load, stability, and the presence of DC offsets at the input. They still have some of these things in mine. I don't have the owners manual. When you first plug it in keep the front panel on/off switch off, this powers the warm up which stays in this mode all the time, then when the amp is put in the on position one led (green) will appear, the right one, the other one left does not go on this use to be the old warm up mode they eliminated for this new upgraded one. After 2 hours it sounds its best. It has 2 fans pulling air from bottom to top with 2 fans on top of each tansistors towers which have cooling fins. It uses bipolar transistors. It has copper binding posts, the best, and high quality inputs jacks. This amp is one of the most open and transparent amplifiers I have heard so its hard for me to sell. You will not be disapointed. It weights 66lbs net. I have the box from when I bought it and packing. Its big boxed: L25", W24", H13" I'm not sure if I will ship it in this box since I may go to a better one..looking at FedEx to ship.