I wasn't able to find out wether or not this has been mentioned before...
Today i found a patch for the "Crackling-Sound-Problem" with a620 and a620 BT available on the ASUS- download-page.
The Patch comes as a zipped cab-file and is dated from 24.may 2004
Anybody who should not have found a workaround to this issue yet can download it.
I tried it myself, it doesn't seem to harm my a620 in any way.

Greetings from sunny Cologne
Wolfgang