Levinson 33H buzzing on standby

Hi All,
I just noticed that my pair of Levinson 33H emits a buzzing sound from the tweeter when it is on Standby (blinking red).

When the amps are turned on, the buzzing sound goes away and is replaced with a slight hissing sound.

When I connect the speakers to my Levinson 433, there is no buzzing...so I'm guessing its not my power/equipment that is causing the problem.

I took the amps into my local service shop and they are telling me that its "normal" behaviour.

Does anyone (perhaps someone with 33Hs) confirm this is normal?

Thanks, Ray