Whoosh sound on power off

I just bought a pair of VTL 450 monoblocks, and everything's good so far except that on power off there's a whoosh type sound coming through the speaker that last for a couple of seconds and then it dies off. I didn't think much of it first but then I noticed it's only coming from one of the monoblocks so it's probably not something normal.

It sounds like it's just the capacitors discharging but it doesn't seem like the sound should leak through the speakers since the other amp's not doing it. Any ideas on what it could be wrong, or is it something that I need to take up with my dealer or VTL?

You might give it some time and see if it's just some latent tube noise that goes away as they break in. Luke Manley is one of the nicest guys around and I'm sure you could call him and get his take.
Jibbonacci, sometimes certain tubes can do that. Its not anything that can damage the amp. In time, you may get audible artifacts from the tube while the amp is playing- that would be the time that I would pay attention. In the meantime- no worries.
Thanks Atmasphere, and it's true I don't notice anything like this while the amp is running. I wouldn't have cared at all about this probably if both amps exhibited the same behaviour. I switched the tubes from the amp that doesn't have this noise on power off to the amp that does and nothing changed... so this leads me to believe that it's not tube related. I'm not really worried about it, it's just something that I'd like to know why is happening.

I actually payed more attention while powering off the other monoblock (that I didn't think had the noise), and if I put my ear on the tweeter I can notice the same faint whoosh sound but it's not nearly as loud.