I had one and I felt the performance did not live up to the sound quality of the A1. Step backward IMHO
I know have a Denon A1SR which is superb. The reason for the change was Yamaha released an upgrade for the AZ1 in Japan to add the new formats but in the UK I was told that I had to go buy the new amp and I should not complain, thus absolutey no concern for the customer who spends out on the flagship product. Hence the change to Denon and I when I told them I will never buy Yamaha again and they did not seem to care they had lost business.
I bought my AZ1 as a stop gap for something more "kick ass". Basically I had a harman/kardon 8500, but had to sell for financial reasons. I found life without decent AV was unbearable so got the AZ1. I thought at the price I bought the AZ1 at (6 month intrest free ) , I would loose little when I sold it for a Pre/Power combo later on.
Little did I know that it would be so good!
The processing is amazing. Totally amazing, actually. Very fast pans and pin point location of sound means that I would rather have this than my old amp. I thought an awful lot about that 8500, rating it better than a Denon A1SR I was demoing at the same time. The Yamaha seems a lot more cinematic than my old 8500 and, looking further back, an AX1 I had too.
Mind you, the AZ1 isn't musical at all and is an AV amp to it's core. It has a brighter presentation than Denon or h/k, though not as bad as sony or Pioneer in this respect. The AZ1 isn't quite as powerful sounding as the 8500, either, but the AZ1 isn't underpowered by a long chalk. The AZ1 does have nearly 80,000 mf of capacitance, so transients can be handles very easily.
I am not interested in music, but can understand that if you are, the AZ1 isn't for you. If you like movies to be presented as they should and can find a gold one, then the AZ1 is a top-notch product that has been overlooked by a lot of people, including me (until now )