[linux-audio-user] ALSA + Envy24HT = High pitched tone

Hi all, Ive come across quite an odd problem. When playing audio via my Revo7.1 card using ALSA, i get a high pitched tone (est ~14khz) mixed with the audio im playing. The tone is constant and is not effected by the volume controls. The tone is only present while an app (for example aplay) is using the card. Some apps cause the tone to be louder thea others (but the tone is of the same constant freq). What makes the problem strange is that if i use JACK to play audio through the card, the tone isnt present at all. Has anyone else come across this problem? BTW, im using the latest kernel (2.6.5) with the ALSA drivers that came with it. Thanks, Mark.