I have been the happy owner of an MX8 (dv852) since April.
(Thread: The last of the MX8-s)

Lately i have been noticing some tiny bursts of "white noise"?

I have included a few samples here:

http://homepage.ntlworld.com/bet.trojak/sounds/

Can anyone shed some light to this?
Can it be a dirty head? (The video quality is good though)
It seems to occur most at rapid changes of volume or pitch on the recording.

Thanks: Bolly

Probably the auto gain adjustments doing its job. The sad news is, being auto, you can't do anything about it.

This auto audio gain, does it makes the sound bad or better?

Same as all things auto, in typical operation, good, in specialised operation, use manual.