question for Luxman L-590AX owners

I own the subject amp, have had it for 3-4 years. I recently noticed a low hum or buzz coming from the amp itself (not the speakers), and would swear that it has been dead quiet up until now. You have to have your head right down beside it to hear it. I'd like to hear what other owners have to say. Are your amps completely quiet? Seems like I may have developed an issue. Thanks in advance, and Merry Christmas.
I have smaller brother... Sister..?  The 550ax2 and a class as well. No hum I've noticed but I'm in a city with good supply and 230v here (which may be a reason) 

As for heat mine gets warm to touch but I can still hold hand to case after hours. A bonus in fact for cold Scotland 
No hum but I’ve trigerred the protection circuit several times now as the amp automatically shut down by itself. The system was played continuously for several hours, sometimes above 10 hours in a day when it happened. At least I am aware the protection circuit feature of the amp is working and the unit is protected from the heat that it produces.

It sounds magnificent by the way.
  1. Buy a DC blocker in Bulgaria , it works fine for me . I,ts a small 122,- dollar investment. Be sure to order the right version...Be sure to order the 2v 6 diodes version.
I have this one, made my Hi-Fi sound better with blacker background and the hum I had from my class A power amp trough my speakers disappeared, mine is with 8 outlets, beautiful made.
The guy behind the company (Mattias) is very friendly and competent, answered a lot of my questions.
Why not shoot him a mail, sure he can help.
I don't have any hum through my speakers, gryphongryph. The piece you linked may be great, but the idea of buying something from halfway around the world for $1000 and seeing if it makes things better isn't overly attractive to me. When my car has an issue, I don't just start replacing parts at random. There has to be a method to the madness, at least for me.