DC-5 crackling, popping noise

[dukelion]

Hi

I've just bought a Mesa/boogie DC-5 combo.
Unfortunately I'm getting a crackling, popping noise when I dial in some gain.

I don't really know a lot about tube amps, cause this is my first one.

I've uploaded a sound clip of the noise here:
http://www.mediafire.com/?z2mnmax3a7t

Theres no guitar connected in that clip. I've checked all the knobs and switches and they don't affect the noise.

Any ideas as to what may be causing this noise?

 

[citizen.one]

it should be valves,at first try preamp, my caliber done something like this too, but it should be by effect cirtuic or bad grounding...