Krell KSA100 doesn't stop upon shut down?

I own a KSA 100 MkI and when I turn it off the sound doesn't stop immediatly but keeps going until vanishes after 20 secondes or so.
Any idea what that could be?
Anything to worry about?
Please note that this amp, which has been recently serviced (capacitores replacment, bias setup, etc) by a Krell expert, doesn't heat up very much either.
Thanks for your help.
Nothing to worry about, quite normal. Even though you've powered off the unit, the unit still has power stored inside and all you are hearing in the discharge.
Like Brf said, normal and nothing to worry about.

IS this common for Krell or everything? I have never had an amp keep playing after the power is turned off.?
Actually, that's an indication that you have big capacitors...since they are holding the charge. When all the power is expended, it doesn't work anymore.
This happens with my SS mono amp and VAC Sig MKIIa preamp ... perfectly normal.
Well, when I turn on my Classe amp there is a slight delay before the amp is ready to play (I can hear a click inside the amp - like a relay closing) So, when it is turned of there is also a click noise inside (about 2 or 3 seconds) after I flip the power switch. I think once you push the power button of, it must seperate the output from the input. I always turn the amp OFF before anything else, but I also mute the preamp first. Maybe sometimes I forget thought- Why are you turning off the amp when it is still getting a signal?
Thank you all for the helpful advice.

6550c, my KRC3 preamp doesn't have an on/off button and my Hybrid CD player I usually leave on to save the warm up time hence if I don't stop the CD from playing, the signal is there. In any case, I indeed usually stop the CD from playing before turning off the amp.
BTW, the only reason to turn the KSA off is obviously its Pure Class A power consumption...
6550C, Classé amps with the exception of a couple multichannel and integrated models, all have output relays. Also, models from the CA series going forward have soft start circuitry that employs relays. They are responsible for the various clicks you hear.

The click after a short delay when you turn your amp on, is the soft start relay(s) contacts closing, to bypass a power resistor in series with the transformer primary. When you turn your amp off, the output relays open almost instantaneously, disconnecting the speakers, and preventing any turn-off thump.

Its apparent from the OP's description, that his amp does not have output relays. Turning an amp off while it is receiving input signal does no harm.
I was a Krell dealer in the early days and had KSA 100s. If it does not heat up much I would have the bias setting checked as class A amps will run hotter at idle than when playing music; the early Krells ran quite warm; one of my KMA 100s blew up twice quite impressively.