Toshiba directv hdtv receiver and Harman Kardon a310 rcvr?
 

I hooked up the optical cable from my Toshiba dst-3000 hdtv receiver for Directv to the optical input of the Harman Kardon A310 optical input and it works fine for the most part but, whenever it encounters channel with dd whether it is 2.0 or 5.1, I hear for a 1/2 second a buzzing sound like when a bug hits a bug zapper light and 1/2 second later, the dd sound comes in ok. Sometimes it makes the sound and other times it does not. I tried a different optical cable but, to no avail. The dd output on the Directv receiver is set to "on" in the audio menu. Toshiba told me yesterday to try a different optical cable but,the buzzing sound is still there. I am only concerned about doing any damage to my Harman Kardon received which I got 2 weeks ago. Any suggestions?

Thanks,

Ian B