USB Sound Card

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Hi there,

I have just made a USB Sound card using a MAX4299 Stereo Amp and a PCM2900E Audio Codec. It didn't work properly at first, and whenever a sound was played a loud crackling sound would play, no matter what the actual output was supposed to be.

After spending ages error-checking and using an oscilloscope to work out where the problem was, I got the card to work perfectly but only if I connected the analog ground of the board to the ground of the oscilloscope. As soon as a I disconnected the oscilloscope ground, all I got was the loud noise again.

Does anyone have any idea why it would only work when attached to the oscilloscope ground, and if there is anything I can do to fix it?

Cheers
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.