On Sat, Jan 28, 2006 at 02:11:50PM +0100, Wolfgang Woehl wrote: > Ok, filter quality. Esben, Fons, on another aspect of > samplerates higher than 48k: Is it possible that what is > audible from an orchestra for example stems in part from > interference or intermodulation of harmonics from above the > audible band? Relevant for the reproduction had the > performance been recorded to discrete channels? > > I don't know how to phrase my question better. Gene said Yes > to that if there was "something non-linear in the mixing > process". I didn't understand that though. There are certainly instruments that produce sound well above 20 kHz. Now to get 'beats' between two of those requires something non-linear - just summing them is not enough. Our ears are non-linear at high sound levels, so in a real performance this could happen. But I don't think it will be noticeable at any sane sound levels. As to non-linearities in the mixing process, that is something that should *not* happen. A properly dithered AD or DA conversion has *no* non-lineraties resulting from the quantisation (until you drive it into saturation). Even at 16 bits it's difficult to get audible intermodulation from the quantisation, unless you are working with pure sinewaves. But some cheap equipment shows very clear non-linear effects, often from the badly designed analog parts, or in the early days of digital, from the converters. It's a long time ago, but I remember having once tested a AD converter that had large 'gaps' - some ranges of values were never used. -- FA
