This isn't a problem exclusive to version 6 of CD Spin Doctor, but it's something that I keep hoping will be addressed. Perhaps there's something wrong with my system(s). I use both a G5 iMac and a 12" G4 Powerbook to record music with CD Spin Doctor.
When I'm recording, it's reassuring to have "listen through speakers" checked, so I can hear what's going into the computer. In an earlier version of CDSD, this would sound garbled/horribly overloaded, although the actual recording would be just fine when played back.
With this latest version, on my iMac, I hear perfect sound -- for about 6 seconds. Then, the sound is replaced by a loud buzzing. The buzzing isn't electrical in nature, like a bad connection; rather, what it sounds like is a few milliseconds of the input sound stuck in a (digital) feedback loop. I can remedy this situation by un-checking and re-checking the "Listen Through Speakers" box -- for about 5-6 seconds, when it'll get "stuck" again.
This happens regardless of which "output device" I have selected, so I don't believe that it's caused by any problems with the USB interface (normally, I play back through a DigiDesign MBox 2, but it happens when I simply play back through my G5 iMac's internal speakers).
Various attempts at googling, or searching these forums, seem to reveal a few other users with similar problems. However, they appear to have difficulty adequately describing the problem, so they generally don't get much help. I'm hoping that my description may be clearer, and thus inspire a solution from someone?