> I have Bob's excellent book and am well aware of the basics (at least) > of summing principals. Although there may be a theoretical benefit to > a higher summing bus resolution, you would have to have something like > 128 tracks at 0db gain to exceed the headroom of a 48bit fixed bus, > and a similar number to exceed the headroom of a 32bit float bus. > > That must be some pretty serious mixing your're doing there if you can > really hear a significant difference! Sorry, in fact a 32bit float bus has a lot less headroom than 48bit fixed (I was thinking 64bit float). However, I'd still maintain that you would need to have considerably more tracks than any typical digital mixer normally has to handle, in order to exceed the available headroom. I'd guess at least 64 tracks at 0db gain, or many hundreds with a more typical dynamic range. I'd certainly be interested to hear some comparisons of mixes where it makes a real difference. BTW - is your soundcard dithering down from 64bit float to your output bit depth? If so, that could be part of any perceived difference? If not, why not? Jules