Does your amp sound hum....when your ear close it

got a concentra 2 , hear hum....when ear close to it
power problem or else? Is it normal?

Can be.....sort of.
Could be a number of things.

Try ""floating the ground" on your amp.
(put the grounded male end into a two prong plug adapter then back into the wall.)
Probably just the transformer(s) doing their stuff. I'm not familiar with this amp, but since you imply that you can't hear the hum until you put your ear next to the amp, not to worry...unless this is your normal listening position!!! Happy Tunes!
If you narrow the hum down to the amplifier's transformer, try to determine which circuit the amplifier is running off of. Then check the circuit breakers in the service panel.

There is the possibility that your amps' circuit is on the opposing leg of some or all of your other audio circuits and therefore generating some AC noise thats affecting the transformer.

Have an electrician move all of your audio circuit breakers in the service panel to the same leg of 115 volts.

Just for grins I moved my amp's circuit over to the opposing leg where my other dedicated audio circuits are to see what sonic improvements I may find. No sonic improvements that I could tell but it cured my transformer hum and the transformer has been almost dead silent every since.
My Rogue 120 magnums hum; I spoke to Mark and he said this is not unusual for tube amps.
You have to be very close, and it has to be very quiet to notice.

My Jolida JD 1000 has a very low level hum. I only hear it when I right on top of it. So, I sit about 8' away and enjoy the music.
Yes, it is normal for your amp to hum, when it doen't know the words.
I put my ear up against my amp, second degree burn on my ear. Dammit
That was the stove silly, not your amp!

My dog suffered a momentary laps of sense when I got down on all 4's to listen for any hum. Boy did he suprise me, that big bastard. My wife hasn't cried from laughing in years!

PS: make sure you don't have any flourecent lights on the same circuit as well as dimmer switches.
Did you hear about the guy who had a fan-cooled amp? When he got close to listen to it hum, it blew in his ear!