The standard for all other amps to follow - solid state and tube alike.

It is wonderful to see and listen to these Beasts but they are not all roses. I work in the business of high end, and for the money spent on a pair I expect them to work. I've seen these amp's blow up. NOT through negligence or abuse but regular use. The tracers on the circuit boards burned off! Audio Reasearch was very good about service, and all damages were warranted. But I would still be very cautious of these amps, 6550 tubes were not designed to be operating in a horizontal placement. With the amount of power and current running through these amps tube failure would be very VERY expensive. For your own piece of mind , if you have the money think long and hard before entering into this Reference because it's much more than just the cost of buying them.

Able to describe it in one word. AWESOME DUDE...:)
If I had the money I'd buy one

These are the best amplifiers in the world! Absolutely no sonic signature to the sound, just music. I was truly amazed by their sound, depth of the bass was unsupassed and made the large Krells seem muddy in comarison. Midrange was totally pure and highs were how they are supposed to sound.The Reference 600 monoblocks, having 600 watts of effortless power, there is no loudspeakers they cannot drive. They are valve amplifiers but do not sound like valve or solid state equipment, nothing at all.
The Audio Research Reference 600s will be my next system upgrade, although it may take a few years to save up a spare $70,000.
6 star rating if I could give it one.