Feedback/buzzing with multichannel card

[decklin]

For testing issue #29, I tried using a USB sound card. Unfortunately, it has 8 channels: 1 thru 6 are the 5.1 surround output and 7/8 are the stereo output that I actually want to use. OS X seems to be able to detect this and plays alert sounds through the stereo output. If I start WavTap normally (quit if it was already running, plug in sound card, select as default, open WavTap.app) I get a weird buzzing sound. This was recorded with some headphones attached to the stereo output and placed next to another computer:

http://www.rupamsunyata.org/decklin/tmp/wavtap-buzzing.flac

You can hear a click sound at the beginning (that's me clicking on WavTap in Applications) and then two at the end (using the menu to quit).

Not sure if this is related to #26 or not. I don't need all 8 channels; I just want the stereo pair to be selected from them.

(I was able to get a cheap 2-channel 48000Hz-only card to work so I think it was just PEBCAK before. However, I don't want to introduce another variable into testing issue #29 -- I may just get another 44100Hz-capable card.)